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C Exercises – Practice Questions with Solutions for C Programming

The best way to learn C programming language is by hands-on practice. This C Exercise page contains the top 30 C exercise questions with solutions that are designed for both beginners and advanced programmers. It covers all major concepts like arrays, pointers, for-loop, and many more.

So, Keep it Up! Solve topic-wise C exercise questions to strengthen your weak topics.

C Programming Exercises

The following are the top 30 programming exercises with solutions to help you practice online and improve your coding efficiency in the C language. You can solve these questions online in GeeksforGeeks IDE.

Q1: Write a Program to Print “Hello World!” on the Console.

In this problem, you have to write a simple program that prints “Hello World!” on the console screen.

For Example,

Click here to view the solution.

Q2: write a program to find the sum of two numbers entered by the user..

In this problem, you have to write a program that adds two numbers and prints their sum on the console screen.

Q3: Write a Program to find the size of int, float, double, and char.

In this problem, you have to write a program to print the size of the variable.

Q4: Write a Program to Swap the values of two variables.

In this problem, you have to write a program that swaps the values of two variables that are entered by the user.

Swap two numbers

Q5: Write a Program to calculate Compound Interest.

In this problem, you have to write a program that takes principal, time, and rate as user input and calculates the compound interest.

Q6: Write a Program to check if the given number is Even or Odd.

In this problem, you have to write a program to check whether the given number is even or odd.

Q7: Write a Program to find the largest number among three numbers.

In this problem, you have to write a program to take three numbers from the user as input and print the largest number among them.

Q8: Write a Program to make a simple calculator.

In this problem, you have to write a program to make a simple calculator that accepts two operands and an operator to perform the calculation and prints the result.

Q9: Write a Program to find the factorial of a given number.

In this problem, you have to write a program to calculate the factorial (product of all the natural numbers less than or equal to the given number n) of a number entered by the user.

Q10: Write a Program to Convert Binary to Decimal.

In this problem, you have to write a program to convert the given binary number entered by the user into an equivalent decimal number.

Q11: Write a Program to print the Fibonacci series using recursion.

In this problem, you have to write a program to print the Fibonacci series(the sequence where each number is the sum of the previous two numbers of the sequence) till the number entered by the user using recursion.

Fibonacci Series

Q12: Write a Program to Calculate the Sum of Natural Numbers using recursion.

In this problem, you have to write a program to calculate the sum of natural numbers up to a given number n.

Q13: Write a Program to find the maximum and minimum of an Array.

In this problem, you have to write a program to find the maximum and the minimum element of the array of size N given by the user.

Q14: Write a Program to Reverse an Array.

In this problem, you have to write a program to reverse an array of size n entered by the user. Reversing an array means changing the order of elements so that the first element becomes the last element and the second element becomes the second last element and so on.

Reverse an array

Q15: Write a Program to rotate the array to the left.

In this problem, you have to write a program that takes an array arr[] of size N from the user and rotates the array to the left (counter-clockwise direction) by D steps, where D is a positive integer.

Q16: Write a Program to remove duplicates from the Sorted array.

In this problem, you have to write a program that takes a sorted array arr[] of size N from the user and removes the duplicate elements from the array.

Q17: Write a Program to search elements in an array (using Binary Search).

In this problem, you have to write a program that takes an array arr[] of size N and a target value to be searched by the user. Search the target value using binary search if the target value is found print its index else print ‘element is not present in array ‘.

Q18: Write a Program to reverse a linked list.

In this problem, you have to write a program that takes a pointer to the head node of a linked list, you have to reverse the linked list and print the reversed linked list.

Q18: Write a Program to create a dynamic array in C.

In this problem, you have to write a program to create an array of size n dynamically then take n elements of an array one by one by the user. Print the array elements.

Q19: Write a Program to find the Transpose of a Matrix.

In this problem, you have to write a program to find the transpose of a matrix for a given matrix A with dimensions m x n and print the transposed matrix. The transpose of a matrix is formed by interchanging its rows with columns.

Q20: Write a Program to concatenate two strings.

In this problem, you have to write a program to read two strings str1 and str2 entered by the user and concatenate these two strings. Print the concatenated string.

Q21: Write a Program to check if the given string is a palindrome string or not.

In this problem, you have to write a program to read a string str entered by the user and check whether the string is palindrome or not. If the str is palindrome print ‘str is a palindrome’ else print ‘str is not a palindrome’. A string is said to be palindrome if the reverse of the string is the same as the string.

Q22: Write a program to print the first letter of each word.

In this problem, you have to write a simple program to read a string str entered by the user and print the first letter of each word in a string.

Q23: Write a program to reverse a string using recursion

In this problem, you have to write a program to read a string str entered by the user, and reverse that string means changing the order of characters in the string so that the last character becomes the first character of the string using recursion.

reverse a string

Q24: Write a program to Print Half half-pyramid pattern.

In this problem, you have to write a simple program to read the number of rows (n) entered by the user and print the half-pyramid pattern of numbers. Half pyramid pattern looks like a right-angle triangle of numbers having a hypotenuse on the right side.

Q25: Write a program to print Pascal’s triangle pattern.

In this problem, you have to write a simple program to read the number of rows (n) entered by the user and print Pascal’s triangle pattern. Pascal’s Triangle is a pattern in which the first row has a single number 1 all rows begin and end with the number 1. The numbers in between are obtained by adding the two numbers directly above them in the previous row.

Pascal’s Triangle

Q26: Write a program to sort an array using Insertion Sort.

In this problem, you have to write a program that takes an array arr[] of size N from the user and sorts the array elements in ascending or descending order using insertion sort.

Q27: Write a program to sort an array using Quick Sort.

In this problem, you have to write a program that takes an array arr[] of size N from the user and sorts the array elements in ascending order using quick sort.

Q28: Write a program to sort an array of strings.

In this problem, you have to write a program that reads an array of strings in which all characters are of the same case entered by the user and sort them alphabetically.

Q29: Write a program to copy the contents of one file to another file.

In this problem, you have to write a program that takes user input to enter the filenames for reading and writing. Read the contents of one file and copy the content to another file. If the file specified for reading does not exist or cannot be opened, display an error message “Cannot open file: file_name” and terminate the program else print “Content copied to file_name”

Q30: Write a program to store information on students using structure.

In this problem, you have to write a program that stores information about students using structure. The program should create various structures, each representing a student’s record. Initialize the records with sample data having data members’ Names, Roll Numbers, Ages, and Total Marks. Print the information for each student.

We hope after completing these C exercises you have gained a better understanding of C concepts. Learning C language is made easier with this exercise sheet as it helps you practice all major C concepts. Solving these C exercise questions will take you a step closer to becoming a C programmer.

Frequently Asked Questions (FAQs)

Q1. what are some common mistakes to avoid while doing c programming exercises.

Some of the most common mistakes made by beginners doing C programming exercises can include missing semicolons, bad logic loops, uninitialized pointers, and forgotten memory frees etc.

Q2. What are the best practices for beginners starting with C programming exercises?

Best practices for beginners starting with C programming exercises: Start with easy codes Practice consistently Be creative Think before you code Learn from mistakes Repeat!

Q3. How do I debug common errors in C programming exercises?

You can use the following methods to debug a code in C programming exercises Read the error message carefully Read code line by line Try isolating the error code Look for Missing elements, loops, pointers, etc Check error online

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Python Practice Problems: Prepare for Your Next Interview

Python Practice Problems: Get Ready for Your Next Interview

Table of Contents

Problem Description

Problem solution.

Are you a Python developer brushing up on your skills before an interview ? If so, then this tutorial will usher you through a series of Python practice problems meant to simulate common coding test scenarios. After you develop your own solutions, you’ll walk through the Real Python team’s answers so you can optimize your code, impress your interviewer, and land your dream job!

In this tutorial, you’ll learn how to:

Write code for interview-style problems
Discuss your solutions during the interview
Work through frequently overlooked details
Talk about design decisions and trade-offs

This tutorial is aimed at intermediate Python developers. It assumes a basic knowledge of Python and an ability to solve problems in Python. You can get skeleton code with failing unit tests for each of the problems you’ll see in this tutorial by clicking on the link below:

Download the sample code: Click here to get the code you’ll use to work through the Python practice problems in this tutorial.

Each of the problems below shows the file header from this skeleton code describing the problem requirements. So download the code, fire up your favorite editor, and let’s dive into some Python practice problems!

Python Practice Problem 1: Sum of a Range of Integers

Let’s start with a warm-up question. In the first practice problem, you’ll write code to sum a list of integers . Each practice problem includes a problem description. This description is pulled directly from the skeleton files in the repo to make it easier to remember while you’re working on your solution.

You’ll see a solution section for each problem as well. Most of the discussion will be in a collapsed section below that. Clone that repo if you haven’t already, work out a solution to the following problem, then expand the solution box to review your work.

Here’s your first problem:

Sum of Integers Up To n ( integersums.py ) Write a function, add_it_up() , that takes a single integer as input and returns the sum of the integers from zero to the input parameter. The function should return 0 if a non-integer is passed in.

Remember to run the unit tests until you get them passing!

Here’s some discussion of a couple of possible solutions.

Note: Remember, don’t open the collapsed section below until you’re ready to look at the answer for this Python practice problem!

Solution for Sum of a Range of Integers Show/Hide

How did writing the solution go? Ready to look at the answer?

For this problem, you’ll look at a few different solutions. The first of these is not so good:

In this solution, you manually build a while loop to run through the numbers 1 through n . You keep a running sum and then return it when you’ve finished the loop.

This solution works, but it has two problems:

It doesn’t display your knowledge of Python and how the language simplifies tasks like this.

It doesn’t meet the error conditions in the problem description. Passing in a string will result in the function throwing an exception when it should just return 0 .

You’ll deal with the error conditions in the final answer below, but first let’s refine the core solution to be a bit more Pythonic .

The first thing to think about is that while loop . Python has powerful mechanisms for iterating over lists and ranges. Creating your own is usually unnecessary, and that’s certainly the case here. You can replace the while loop with a loop that iterates over a range() :

You can see that the for...range() construct has replaced your while loop and shortened the code. One thing to note is that range() goes up to but does not include the number given, so you need to use n + 1 here.

This was a nice step! It removes some of the boilerplate code of looping over a range and makes your intention clearer. But there’s still more you can do here.

Summing a list of integers is another thing Python is good at:

Wow! By using the built-in sum() , you got this down to one line of code! While code golf generally doesn’t produce the most readable code, in this case you have a win-win: shorter and more readable code.

There’s one problem remaining, however. This code still doesn’t handle the error conditions correctly. To fix that, you can wrap your previous code in a try...except block:

This solves the problem and handles the error conditions correctly. Way to go!

Occasionally, interviewers will ask this question with a fixed limit, something like “Print the sum of the first nine integers.” When the problem is phrased that way, one correct solution would be print(45) .

If you give this answer, however, then you should follow up with code that solves the problem step by step. The trick answer is a good place to start your answer, but it’s not a great place to end.

If you’d like to extend this problem, try adding an optional lower limit to add_it_up() to give it more flexibility!

Python Practice Problem 2: Caesar Cipher

The next question is a two-parter. You’ll code up a function to compute a Caesar cipher on text input. For this problem, you’re free to use any part of the Python standard library to do the transform.

Hint: There’s a function in the str class that will make this task much easier!

The problem statement is at the top of the skeleton source file:

Caesar Cipher ( caesar.py ) A Caesar cipher is a simple substitution cipher in which each letter of the plain text is substituted with a letter found by moving n places down the alphabet. For example, assume the input plain text is the following: abcd xyz If the shift value, n , is 4, then the encrypted text would be the following: efgh bcd You are to write a function that accepts two arguments, a plain-text message and a number of letters to shift in the cipher. The function will return an encrypted string with all letters transformed and all punctuation and whitespace remaining unchanged. Note: You can assume the plain text is all lowercase ASCII except for whitespace and punctuation.

Remember, this part of the question is really about how well you can get around in the standard library. If you find yourself figuring out how to do the transform without the library, then save that thought! You’ll need it later!

Here’s a solution to the Caesar cipher problem described above.

Note: Remember, don’t open the collapsed section below until you’re ready to look at the answers for this Python practice problem!

Solution for Caesar Cipher Show/Hide

This solution makes use of .translate() from the str class in the standard library. If you struggled with this problem, then you might want to pause a moment and consider how you could use .translate() in your solution.

Okay, now that you’re ready, let’s look at this solution:

You can see that the function makes use of three things from the string module:

.ascii_lowercase
.maketrans()
.translate()

In the first two lines, you create a variable with all the lowercase letters of the alphabet (ASCII only for this program) and then create a mask , which is the same set of letters, only shifted. The slicing syntax is not always obvious, so let’s walk through it with a real-world example:

You can see that x[3:] is all the letters after the third letter, 'c' , while x[:3] is just the first three letters.

Line 6 in the solution, letters[shift_num:] + letters[:shift_num] , creates a list of letters shifted by shift_num letters, with the letters at the end wrapped around to the front. Once you have the list of letters and the mask of letters you want to map to, you call .maketrans() to create a translation table.

Next, you pass the translation table to the string method .translate() . It maps all characters in letters to the corresponding letters in mask and leaves all other characters alone.

This question is an exercise in knowing and using the standard library. You may be asked a question like this at some point during an interview. If that happens to you, it’s good to spend some time thinking about possible answers. If you can remember the method— .translate() in this case—then you’re all set.

But there are a couple of other scenarios to consider:

You may completely draw a blank. In this case, you’ll probably solve this problem the way you solve the next one , and that’s an acceptable answer.

You may remember that the standard library has a function to do what you want but not remember the details.

If you were doing normal work and hit either of these situations, then you’d just do some searching and be on your way. But in an interview situation, it will help your cause to talk through the problem out loud.

Asking the interviewer for specific help is far better than just ignoring it. Try something like “I think there’s a function that maps one set of characters to another. Can you help me remember what it’s called?”

In an interview situation, it’s often better to admit that you don’t know something than to try to bluff your way through.

Now that you’ve seen a solution using the Python standard library, let’s try the same problem again, but without that help!

Python Practice Problem 3: Caesar Cipher Redux

For the third practice problem, you’ll solve the Caesar cipher again, but this time you’ll do it without using .translate() .

The description of this problem is the same as the previous problem. Before you dive into the solution, you might be wondering why you’re repeating the same exercise, just without the help of .translate() .

That’s a great question. In normal life, when your goal is to get a working, maintainable program, rewriting parts of the standard library is a poor choice. The Python standard library is packed with working, well-tested, and fast solutions for problems large and small. Taking full advantage of it is a mark of a good programmer.

That said, this is not a work project or a program you’re building to satisfy a need. This is a learning exercise, and it’s the type of question that might be asked during an interview. The goal for both is to see how you can solve the problem and what interesting design trade-offs you make while doing it.

So, in the spirit of learning, let’s try to resolve the Caesar cipher without .translate() .

For this problem, you’ll have two different solutions to look at when you’re ready to expand the section below.

Solutions for Caesar Cipher Redux Show/Hide

For this problem, two different solutions are provided. Check out both and see which one you prefer!

For the first solution, you follow the problem description closely, adding an amount to each character and flipping it back to the beginning of the alphabet when it goes on beyond z :

Starting on line 14, you can see that caesar() does a list comprehension , calling a helper function for each letter in message . It then does a .join() to create the new encoded string. This is short and sweet, and you’ll see a similar structure in the second solution. The interesting part happens in shift_n() .

Here you can see another use for string.ascii_lowercase , this time filtering out any letter that isn’t in that group. Once you’re certain you’ve filtered out any non-letters, you can proceed to encoding. In this version of encoding, you use two functions from the Python standard library:

Again, you’re encouraged not only to learn these functions but also to consider how you might respond in an interview situation if you couldn’t remember their names.

ord() does the work of converting a letter to a number, and chr() converts it back to a letter. This is handy as it allows you to do arithmetic on letters, which is what you want for this problem.

The first step of your encoding on line 7 gets the numeric value of the encoded letter by using ord() to get the numeric value of the original letter. ord() returns the Unicode code point of the character, which turns out to be the ASCII value.

For many letters with small shift values, you can convert the letter back to a character and you’ll be done. But consider the starting letter, z .

A shift of one character should result in the letter a . To achieve this wraparound, you find the difference from the encoded letter to the letter z . If that difference is positive, then you need to wrap back to the beginning.

You do this in lines 8 to 11 by repeatedly adding 26 to or subtracting it from the character until it’s in the range of ASCII characters. Note that this is a fairly inefficient method for fixing this issue. You’ll see a better solution in the next answer.

Finally, on line 12, your conversion shift function takes the numeric value of the new letter and converts it back to a letter to return it.

While this solution takes a literal approach to solving the Caesar cipher problem, you could also use a different approach modeled after the .translate() solution in practice problem 2 .

The second solution to this problem mimics the behavior of Python’s built-in method .translate() . Instead of shifting each letter by a given amount, it creates a translation map and uses it to encode each letter:

Starting with caesar() on line 11, you start by fixing the problem of amount being greater than 26 . In the previous solution, you looped repeatedly until the result was in the proper range. Here, you take a more direct and more efficient approach using the mod operator ( % ).

The mod operator produces the remainder from an integer division. In this case, you divide by 26 , which means the results are guaranteed to be between 0 and 25 , inclusive.

Next, you create the translation table. This is a change from the previous solutions and is worth some attention. You’ll see more about this toward the end of this section.

Once you create the table , the rest of caesar() is identical to the previous solution: a list comprehension to encrypt each letter and a .join() to create a string.

shift_n() finds the index of the given letter in the alphabet and then uses this to pull a letter from the table . The try...except block catches those cases that aren’t found in the list of lowercase letters.

Now let’s discuss the table creation issue. For this toy example, it probably doesn’t matter too much, but it illustrates a situation that occurs frequently in everyday development: balancing clarity of code against known performance bottlenecks.

If you examine the code again, you’ll see that table is used only inside shift_n() . This indicates that, in normal circumstances, it should have been created in, and thus have its scope limited to, shift_n() :

The issue with that approach is that it spends time calculating the same table for every letter of the message. For small messages, this time will be negligible, but it might add up for larger messages.

Another possible way that you could avoid this performance penalty would be to make table a global variable . While this also cuts down on the construction penalty, it makes the scope of table even larger. This doesn’t seem better than the approach shown above.

At the end of the day, the choice between creating table once up front and giving it a larger scope or just creating it for every letter is what’s called a design decision . You need to choose the design based on what you know about the actual problem you’re trying to solve.

If this is a small project and you know it will be used to encode large messages, then creating the table only once could be the right decision. If this is only a portion of a larger project, meaning maintainability is key, then perhaps creating the table each time is the better option.

Since you’ve looked at two solutions, it’s worth taking a moment to discuss their similarities and differences.

Solution Comparison

You’ve seen two solutions in this part of the Caesar cipher, and they’re fairly similar in many ways. They’re about the same number of lines. The two main routines are identical except for limiting amount and creating table . It’s only when you look at the two versions of the helper function, shift_n() , that the differences appear.

The first shift_n() is an almost literal translation of what the problem is asking for: “Shift the letter down the alphabet and wrap it around at z .” This clearly maps back to the problem statement, but it has a few drawbacks.

Although it’s about the same length as the second version, the first version of shift_n() is more complex. This complexity comes from the letter conversion and math needed to do the translation. The details involved—converting to numbers, subtracting, and wrapping—mask the operation you’re performing. The second shift_n() is far less involved in its details.

The first version of the function is also specific to solving this particular problem. The second version of shift_n() , like the standard library’s .translate() that it’s modeled after, is more general-purpose and can be used to solve a larger set of problems. Note that this is not necessarily a good design goal.

One of the mantras that came out of the Extreme Programming movement is “You aren’t gonna need it” (YAGNI). Frequently, software developers will look at a function like shift_n() and decide that it would be better and more general-purpose if they made it even more flexible, perhaps by passing in a parameter instead of using string.ascii_lowercase .

While that would indeed make the function more general-purpose, it would also make it more complex. The YAGNI mantra is there to remind you not to add complexity before you have a specific use case for it.

To wrap up your Caesar cipher section, there are clear trade-offs between the two solutions, but the second shift_n() seems like a slightly better and more Pythonic function.

Now that you’ve written the Caesar cipher three different ways, let’s move on to a new problem.

Python Practice Problem 4: Log Parser

The log parser problem is one that occurs frequently in software development. Many systems produce log files during normal operation, and sometimes you’ll need to parse these files to find anomalies or general information about the running system.

For this problem, you’ll need to parse a log file with a specified format and generate a report:

Log Parser ( logparse.py ) Accepts a filename on the command line. The file is a Linux-like log file from a system you are debugging. Mixed in among the various statements are messages indicating the state of the device. They look like this: Jul 11 16:11:51:490 [139681125603136] dut: Device State: ON The device state message has many possible values, but this program cares about only three: ON , OFF , and ERR . Your program will parse the given log file and print out a report giving how long the device was ON and the timestamp of any ERR conditions.

Note that the provided skeleton code doesn’t include unit tests. This was omitted since the exact format of the report is up to you. Think about and write your own during the process.

A test.log file is included, which provides you with an example. The solution you’ll examine produces the following output:

While that format is generated by the Real Python solution, you’re free to design your own format for the output. The sample input file should generate equivalent information.

In the collapsed section below, you’ll find a possible solution to the log parser problem. When you’re ready, expand the box and compare it with what you came up with!

Solution for Log Parser Problem Show/Hide

Full Solution

Since this solution is longer than what you saw for the integer sums or the Caesar cipher problems, let’s start with the full program:

That’s your full solution. You can see that the program consists of three functions and the main section. You’ll work through them from the top.

Helper Function: get_next_event()

First up is get_next_event() :

Because it contains a yield statement, this function is a generator . That means you can use it to generate one event from the log file at a time.

You could have just used for line in datafile , but instead you add a little bit of filtering. The calling routine will get only those events that have dut: Device State: in them. This keeps all the file-specific parsing contained in a single function.

This might make get_next_event() a bit more complicated, but it’s a relatively small function, so it remains short enough to read and comprehend. It also keeps that complicated code encapsulated in a single location.

You might be wondering when datafile gets closed. As long as you call the generator until all of the lines are read from datafile , the for loop will complete, allowing you to leave the with block and exit from the function.

Helper Function: compute_time_diff_seconds()

The second function is compute_time_diff_seconds() , which, as the name suggests, computes the number of seconds between two timestamps:

There are a few interesting points to this function. The first is that subtracting the two datetime objects results in a datetime.timedelta . For this problem, you will report total seconds, so returning .total_seconds() from the timedelta is appropriate.

The second item of note is that there are many, many packages in Python that simplify handling dates and times. In this case, your use model is simple enough that it doesn’t warrant the complexity of pulling in an external library when the standard library functions will suffice.

That said, datetime.datetime.strptime() is worthy of mention. When passed a string and a specific format, .strptime() parses that string with the given format and produces a datetime object.

This is another place where, in an interview situation, it’s important not to panic if you can’t remember the exact names of the Python standard library functions.

Helper Function: extract_data()

Next up is extract_data() , which does the bulk of the work in this program. Before you dive into the code, let’s step back and talk about state machines.

State machines are software (or hardware) devices that transition from one state to another depending on specific inputs. That’s a really broad definition that might be difficult to grasp, so let’s look at a diagram of the state machine you’ll be using below:

State machine with two states: ON and OFF with transitions between the states.

In this diagram, the states are represented by the labeled boxes. There are only two states here, ON and OFF , which correspond to the state of the device. There are also two input signals, Device State: ON and Device State: OFF . The diagram uses arrows to show what happens when an input occurs while the machine is in each state.

For example, if the machine is in the ON state and the Device State: ON input occurs, then the machine stays in the ON state. No change happens. Conversely, if the machine receives the Device State: OFF input when it’s in the ON state, then it will transition to the OFF state.

While the state machine here is only two states with two inputs, state machines are often much more complex. Creating a diagram of expected behavior can help you make the code that implements the state machine more concise.

Let’s move back to extract_data() :

It might be hard to see the state machine here. Usually, state machines require a variable to hold the state. In this case, you use time_on_started to serve two purposes:

Indicate state: time_on_started holds the state of your state machine. If it’s None , then the machine is in the OFF state. If it’s not None , then the machine is ON .
Store start time: If the state is ON , then time_on_started also holds the timestamp of when the device turned on. You use this timestamp to call compute_time_diff_seconds() .

The top of extract_data() sets up your state variable, time_on_started , and also the two outputs you want. errs is a list of timestamps at which the ERR message was found, and total_time_on is the sum of all periods when the device was on.

Once you’ve completed the initial setup, you call the get_next_event() generator to retrieve each event and timestamp. The action it receives is used to drive the state machine, but before it checks for state changes, it first uses an if block to filter out any ERR conditions and add those to errs .

After the error check, the first elif block handles transitions to the ON state. You can transition to ON only when you’re in the OFF state, which is signaled by time_on_started being False . If you’re not already in the ON state and the action is "ON" , then you store the timestamp , putting the machine into the ON state.

The second elif handles the transition to the OFF state. On this transition, extract_data() needs to compute the number of seconds the device was on. It does this using the compute_time_diff_seconds() you saw above. It adds this time to the running total_time_on and sets time_on_started back to None , effectively putting the machine back into the OFF state.

Main Function

Finally, you can move on to the __main__ section. This final section passes sys.argv[1] , which is the first command-line argument , to extract_data() and then presents a report of the results:

To call this solution, you run the script and pass the name of the log file. Running your example code results in this output:

Your solution might have different formatting, but the information should be the same for the sample log file.

There are many ways to solve a problem like this. Remember that in an interview situation, talking through the problem and your thought process can be more important than which solution you choose to implement.

That’s it for the log-parsing solution. Let’s move on to the final challenge: sudoku!

Python Practice Problem 5: Sudoku Solver

Your final Python practice problem is to solve a sudoku puzzle!

Finding a fast and memory-efficient solution to this problem can be quite a challenge. The solution you’ll examine has been selected for readability rather than speed, but you’re free to optimize your solution as much as you want.

The description for the sudoku solver is a little more involved than the previous problems:

Sudoku Solver ( sudokusolve.py ) Given a string in SDM format, described below, write a program to find and return the solution for the sudoku puzzle in the string. The solution should be returned in the same SDM format as the input. Some puzzles will not be solvable. In that case, return the string “Unsolvable”. The general SDM format is described here . For our purposes, each SDM string will be a sequence of 81 digits, one for each position on the sudoku puzzle. Known numbers will be given, and unknown positions will have a zero value. For example, assume you’re given this string of digits: 004006079000000602056092300078061030509000406020540890007410920105000000840600100 The string represents this starting sudoku puzzle: 0 0 4 0 0 6 0 7 9 0 0 0 0 0 0 6 0 2 0 5 6 0 9 2 3 0 0 0 7 8 0 6 1 0 3 0 5 0 9 0 0 0 4 0 6 0 2 0 5 4 0 8 9 0 0 0 7 4 1 0 9 2 0 1 0 5 0 0 0 0 0 0 8 4 0 6 0 0 1 0 0 The provided unit tests may take a while to run, so be patient. Note: A description of the sudoku puzzle can be found on Wikipedia .

You can see that you’ll need to deal with reading and writing to a particular format as well as generating a solution.

When you’re ready, you can find a detailed explanation of a solution to the sudoku problem in the box below. A skeleton file with unit tests is provided in the repo.

Solution for Sudoku Solver Show/Hide

This is a larger and more complex problem than you’ve looked at so far in this tutorial. You’ll walk through the problem step by step, ending with a recursive function that solves the puzzle. Here’s a rough outline of the steps you’ll take:

Read the puzzle into a grid form.
Place the number in the cell.
Remove that number from the row, column, and small square.
Move to the next position.
If no possible numbers remain, then declare the puzzle unsolvable .
If all cells are filled, then return the solution .

The tricky part of this algorithm is keeping track of the grid at each step of the process. You’ll use recursion, making a new copy of the grid at each level of the recursion, to maintain this information.

With that outline in mind, let’s start with the first step, creating the grid.

Generating a Grid From a Line

To start, it’s helpful to convert the puzzle data into a more usable format. Even if you eventually want to solve the puzzle in the given SDM format , you’ll likely make faster progress working through the details of your algorithm with the data in a grid form. Once you have a solution that works, then you can convert it to work on a different data structure.

To this end, let’s start with a couple of conversion functions:

Your first function, line_to_grid() , converts the data from a single string of eighty-one digits to a list of lists. For example, it converts the string line to a grid like start :

Each inner list here represents a horizontal row in your sudoku puzzle.

You start with an empty grid and an empty line . You then build each line by converting nine characters from the values string to single-digit integers and then appending them to the current line . Once you have nine values in a line , as indicated by index % 9 == 0 on line 7, you insert that line into the grid and start a new one.

The function ends by appending the final line to the grid . You need this because the for loop will end with the last line still stored in the local variable and not yet appended to grid .

The inverse function, grid_to_line() , is slightly shorter. It uses a generator expression with .join() to create a nine-digit string for each row. It then appends that string to the overall line and returns it. Note that it’s possible to use nested generators to create this result in fewer lines of code, but the readability of the solution starts to fall off dramatically.

Now that you’ve got the data in the data structure you want, let’s start working with it.

Generating a Small Square Iterator

Your next function is a generator that will help you search for the smaller three-by-three square a given position is in. Given the x- and y-coordinates of the cell in question, this generator will produce a list of coordinates that match the square that contains it:

A Sudoku grid with one of the small squares highlighted.

In the image above, you’re examining cell (3, 1) , so your generator will produce coordinate pairs corresponding to all the lightly shaded cells, skipping the coordinates that were passed in:

Putting the logic for determining this small square in a separate utility function keeps the flow of your other functions more readable. Making this a generator allows you to use it in a for loop to iterate through each of the values.

The function to do this involves using the limitations of integer math:

There are a lot of threes in a couple of those lines, which makes lines like ((x + 3) // 3) * 3 look confusing. Here’s what happens when x is 1 .

Using the rounding of integer math allows you to get the next-highest multiple of three above a given value. Once you have this, subtracting three will give you the multiple of three below the given number.

There are a few more low-level utility functions to examine before you start building on top of them.

Moving to the Next Spot

Your solution will need to walk through the grid structure one cell at a time. This means that at some point, you’ll need to figure out what the next position should be. compute_next_position() to the rescue!

compute_next_position() takes the current x- and y-coordinates as input and returns a tuple containing a finished flag along with the x- and y-coordinates of the next position:

The finished flag tells the caller that the algorithm has walked off the end of the puzzle and has completed all the squares. You’ll see how that’s used in a later section.

Removing Impossible Numbers

Your final low-level utility is quite small. It takes an integer value and an iterable. If the value is nonzero and appears in the iterable, then the function removes it from the iterable:

Typically, you wouldn’t make this small bit of functionality into a function. You’ll use this function several times, though, so it’s best to follow the DRY principle and pull it up to a function.

Now you’ve seen the bottom level of the functionality pyramid. It’s time to step up and use those tools to build a more complex function. You’re almost ready to solve the puzzle!

Finding What’s Possible

Your next function makes use of some of the low-level functions you’ve just walked through. Given a grid and a position on that grid, it determines what values that position could still have:

A Sudoku grid showing a starting point to indicate possible values for a specific cell.

For the grid above, at the position (3, 1) , the possible values are [1, 5, 8] because the other values are all present, either in that row or column or in the small square you looked at earlier.

This is the responsibility of detect_possible() :

The function starts by checking if the given position at x and y already has a nonzero value. If so, then that’s the only possible value and it returns.

If not, then the function creates a set of the numbers one through nine. The function proceeds to check different blocking numbers and removes those from this set.

It starts by checking the column and row of the given position. This can be done with a single loop by just alternating which subscript changes. grid[x][index] checks values in the same column, while grid[index][y] checks those values in the same row. You can see that you’re using test_and_remove() here to simplify the code.

Once those values have been removed from your possible set, the function moves on to the small square. This is where the small_square() generator you created before comes in handy. You can use it to iterate over each position in the small square, again using test_and_remove() to eliminate any known values from your possible list.

Once all the known blocking values have been removed from your set, you have the list of all possible values for that position on that grid.

You might wonder why the code and its description make a point about the position being “on that grid.” In your next function, you’ll see that the program makes many copies of the grid as it tries to solve it.

You’ve reached the heart of this solution: solve() ! This function is recursive, so a little up-front explanation might help.

The general design of solve() is based on testing a single position at a time. For the position of interest, the algorithm gets the list of possible values and then selects those values, one at a time, to be in this position.

For each of these values, it creates a grid with the guessed value in this position. It then calls a function to test for a solution, passing in the new grid and the next position.

It just so happens that the function it calls is itself.

For any recursion, you need a termination condition. This algorithm has four of them:

There are no possible values for this position. That indicates the solution it’s testing can’t work.
It’s walked to the end of the grid and found a possible value for each position. The puzzle is solved!
One of the guesses at this position, when passed back to the solver, returns a solution.
It’s tried all possible values at this position and none of them will work.

Let’s look at the code for this and see how it all plays out:

The first thing to note in this function is that it makes a .deepcopy() of the grid. It does a deep copy because the algorithm needs to keep track of exactly where it was at any point in the recursion. If the function made only a shallow copy, then every recursive version of this function would use the same grid.

Once the grid is copied, solve() can work with the new copy, temp . A position on the grid was passed in, so that’s the number that this version of the function will solve. The first step is to see what values are possible in this position. As you saw earlier, detect_possible() returns a list of possible values that may be empty.

If there are no possible values, then you’ve hit the first termination condition for the recursion. The function returns False , and the calling routine moves on.

If there are possible values, then you need to move on and see if any of them is a solution. Before you do that, you can add a little optimization to the code. If there’s only a single possible value, then you can insert that value and move on to the next position. The solution shown does this in a loop, so you can place multiple numbers into the grid without having to recur.

This may seem like a small improvement, and I’ll admit my first implementation did not include this. But some testing showed that this solution was dramatically faster than simply recurring here at the price of more complex code.

Note: This is an excellent point to bring up during an interview even if you don’t add the code to do this. Showing them that you’re thinking about trading off speed against complexity is a strong positive signal to interviewers.

Sometimes, of course, there will be multiple possible values for the current position, and you’ll need to decide if any of them will lead to a solution. Fortunately, you’ve already determined the next position in the grid, so you can forgo placing the possible values.

If the next position is off the end of the grid, then the current position is the final one to fill. If you know that there’s at least one possible value for this position, then you’ve found a solution! The current position is filled in and the completed grid is returned up to the calling function.

If the next position is still on the grid, then you loop through each possible value for the current spot, filling in the guess at the current position and then calling solve() with the temp grid and the new position to test.

solve() can return only a completed grid or False , so if any of the possible guesses returns a result that isn’t False , then a result has been found, and that grid can be returned up the stack.

If all possible guesses have been made and none of them is a solution, then the grid that was passed in is unsolvable. If this is the top-level call, then that means the puzzle is unsolvable. If the call is lower in the recursion tree, then it just means that this branch of the recursion tree isn’t viable.

Putting It All Together

At this point, you’re almost through the solution. There’s only one final function left, sudoku_solve() :

This function does three things:

Converts the input string into a grid
Calls solve() with that grid to get a solution
Returns the solution as a string or "Unsolvable" if there’s no solution

That’s it! You’ve walked through a solution for the sudoku solver problem.

Interview Discussion Topics

The sudoku solver solution you just walked through is a good deal of code for an interview situation. Part of an interview process would likely be to discuss some of the code and, more importantly, some of the design trade-offs you made. Let’s look at a few of those trade-offs.

The biggest design decision revolves around using recursion. It’s possible to write a non-recursive solution to any problem that has a recursive solution. Why choose recursion over another option?

This is a discussion that depends not only on the problem but also on the developers involved in writing and maintaining the solution. Some problems lend themselves to rather clean recursive solutions, and some don’t.

In general, recursive solutions will take more time to run and use more memory than non-recursive solutions. But that’s not always true and, more importantly, it’s not always important .

Similarly, some teams of developers are comfortable with recursive solutions, while others find them exotic or unnecessarily complex. Maintainability should play into your design decisions as well.

One good discussion to have about a decision like this is around performance. How fast does this solution need to execute? Will it be used to solve billions of puzzles or just a handful? Will it run on a small embedded system with memory constraints, or will it be on a large server?

These external factors can help you decide which is a better design decision. These are great topics to bring up in an interview as you’re working through a problem or discussing code. A single product might have places where performance is critical (doing ray tracing on a graphics algorithm, for example) and places where it doesn’t matter at all (such as parsing the version number during installation).

Bringing up topics like this during an interview shows that you’re not only thinking about solving an abstract problem, but you’re also willing and able to take it to the next level and solve a specific problem facing the team.

Readability and Maintainability

Sometimes it’s worth picking a solution that’s slower in order to make a solution that’s easier to work with, debug, and extend. The decision in the sudoku solver challenge to convert the data structure to a grid is one of those decisions.

That design decision likely slows down the program, but unless you’ve measured, you don’t know. Even if it does, putting the data structure into a form that’s natural for the problem can make the code easier to comprehend.

It’s entirely possible to write a solver that operates on the linear strings you’re given as input. It’s likely faster and probably takes less memory, but small_square() , among others, will be a lot harder to write, read, and maintain in this version.

Another thing to discuss with an interviewer, whether you’re live coding or discussing code you wrote offline, is the mistakes and false turns you took along the way.

This is a little less obvious and can be slightly detrimental, but particularly if you’re live coding, taking a step to refactor code that isn’t right or could be better can show how you work. Few developers can write perfect code the first time. Heck, few developers can write good code the first time.

Good developers write the code, then go back and refactor it and fix it. For example, my first implementation of detect_possible() looked like this:

Ignoring that it doesn’t consider the small_square() information, this code can be improved. If you compare this to the final version of detect_possible() above, you’ll see that the final version uses a single loop to test both the horizontal and the vertical dimensions.

Wrapping Up

That’s your tour through a sudoku solver solution. There’s more information available on formats for storing puzzles and a huge list of sudoku puzzles you can test your algorithm on.

That’s the end of your Python practice problems adventure! But if you’d like more, head on over to the video course Write and Test a Python Function: Interview Practice to see an experienced developer tackle an interview problem in real time.

Congratulations on working through this set of Python practice problems! You’ve gotten some practice applying your Python skills and also spent some time thinking about how you can respond in different interviewing situations.

In this tutorial, you learned how to:

Remember, you can download the skeleton code for these problems by clicking on the link below:

Feel free to reach out in the comments section with any questions you have or suggestions for other Python practice problems you’d like to see! Also check out our “Ace Your Python Coding Interview” Learning Path to get more resources and for boosting your Python interview skills.

Good luck with the interview!

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Python Basic Exercise for Beginners

Updated on: August 29, 2024 | 498 Comments

This essential Python exercise helps Python beginners learn necessary Python skills quickly.

Immerse yourself in the practice of Python’s foundational concepts, such as loops, control flow, data types, operators, list, strings, input-output, and built-in functions. This beginner’s exercise is sure to elevate your understanding of Python.

Also, See :

Python Quizzes : Solve quizzes to test your knowledge of fundamental concepts.
Python Basics : Learn the basics to solve this exercise.

What questions are included in this Python fundamental exercise?

The exercise contains 15 Python programs to solve , ranging from beginner to intermediate difficulty.
The hints and solutions are provided for each question.
Tips and essential learning resources accompany each question . These will assist you in solving the exercise and empower you with the knowledge to tackle similar problems in the future, boosting your confidence and capability. As you progress, you’ll become more familiar with the basics of Python.

Use Online Code Editor to solve exercises.

This Python exercise covers questions on the following topics :

Python for loop and while loop
Python list , set , tuple , dictionary , input, and output

Also, try to solve the basic Python Quiz for beginners

Exercise 1: Calculate the multiplication and sum of two numbers

Given two integer numbers, write a Python code to return their product only if the product is equal to or lower than 1000. Otherwise, return their sum.

Expected Output :

Accept user input in Python
Calculate an Average in Python
Create a function that will take two numbers as parameters
Next, Inside a function, multiply two numbers and save their product in a product variable
Next, use the if condition to check if the product >1000 . If yes, return the product
Otherwise, use the else block to calculate the sum of two numbers and return it.

Exercise 2: Print the Sum of a Current Number and a Previous number

Write a Python code to iterate the first 10 numbers, and in each iteration, print the sum of the current and previous number.

Reference article for help :

Python range() function
Calculate sum and average in Python
Create a variable called previous_num and assigning it to 0
Next, iterate through the first 10 numbers using the for loop and range() function
Next, display the current number ( i ), the previous number, and the addition of both numbers in each iteration of a loop
Finally, you need to update the previous_num for the next iteration. To do this, assign the value of the current number to the previous number ( previous_num = i).

Exercise 3: Print characters present at an even index number

Write a Python code to accept a string from the user and display characters present at an even index number.

For example, str = "PYnative" . so your code should display ‘P’, ‘n’, ‘t’, ‘v’.

Reference article for help: Python Input and Output

Use the Python input() function to accept a string from a user.
Calculate the length of the string using the len() function
Next, iterate characters of a string using the loop and range() function.
Use start = 0, stop = len(s)-1, and step =2. the step is 2 because we want only even index numbers
In each iteration of a loop, use s[i] to print characters present at the current even index number

Solution 1 :

Solution 2 : Using list slicing

Exercise 4: Remove first n characters from a string

Write a Python code to remove characters from a string from 0 to n and return a new string.

For Example:

remove_chars("PYnative", 4) so output must be tive . Here, you need to remove the first four characters from a string.
remove_chars("PYnative", 2) so output must be native . Here, you need to remove the first two characters from a string.

Note : n must be less than the length of the string.

Use string slicing to get a substring. For example, remove the first four characters using s[4:] .

Also, try to solve Python string exercises

Exercise 5: Check if the first and last numbers of a list are the same

Write a code to return True if the list’s first and last numbers are the same. If the numbers are different, return False .

Exercise 6: Display numbers divisible by 5

Write a Python code to display numbers from a list divisible by 5

Also, try to solve Python list Exercise

Exercise 7: Find the number of occurrences of a substring in a string

Write a Python code to find how often the substring “ Emma ” appears in the given string.

Use string method count() .

Solution 1 : Use the count() method

Solution 2 : Without the string method

Exercise 8: Print the following pattern

Hint : Print Pattern using for loop

Exercise 9: Check Palindrome Number

Write a Python code to check if the given number is palindrome. A palindrome number is a number that is the same after reverse. For example, 545 is the palindrome number .

Reverse the given number and save it in a different variable
Use the if condition to check if the original and reverse numbers are identical. If yes, return True .

Exercise 10: Merge two lists using the following condition

Given two lists of numbers, write a Python code to create a new list such that the latest list should contain odd numbers from the first list and even numbers from the second list .

Create an empty list named result_list
Iterate the first list using a for loop
In each iteration check if the current number is odd using the num % 2 != 0 formula. If the current number is odd, add it to the result list
Now, Iterate the second list using a loop.
In each iteration check if the current number is even using the num % 2 == 0 formula. If the current number is even, add it to the result list.
Print the result list.

Note: Try to solve the Python list exercises

Exercise 11: Get each digit from a number in the reverse order.

For example, If the given integer number is 7536 , the output shall be “ 6 3 5 7 “, with a space separating the digits.

Use while loop

Exercise 12: Calculate income tax

Calculate income tax for the given income by adhering to the rules below

Taxable Income	Rate (in %)
First $10,000	0
Next $10,000	10
The remaining	20

For example, suppose the income is 45000, and the income tax payable is

10000*0% + 10000*10% + 25000*20% = $6000.

Exercise 13: Print multiplication table from 1 to 10

See : How to use nested loops in Python

Create the outer for loop to iterate numbers from 1 to 10. Thus, the outer loop’s total number of iterations is 10.
Create an inner loop to iterate 10 times.
For each outer loop iteration, the inner loop will execute 10 times.
The number is 1 in the first iteration of the outer loop. In the next, it is 2, and so on until it reaches 10.
In each iteration of an inner loop, we perform a simple calculation: the multiplication of two numbers. (current outer number and current inner number)

Exercise 14: Print a downward half-pyramid pattern of stars

Exercise 15: get an int value of base raises to the power of exponent.

Write a function called exponent(base, exp) that returns an int value of base raises to the power of exp.

Note here exp is a non-negative integer, and the base is an integer.

Expected output

I want to hear from you. What do you think of this essential exercise? If you have better alternative answers to the above questions, please help others by commenting on this exercise.

I have shown only 15 questions in this exercise because we have Topic-specific exercises to cover each topic exercise in detail. Please refer to all Python exercises .

Did you find this page helpful? Let others know about it. Sharing helps me continue to create free Python resources.

About Vishal

I’m Vishal Hule , the Founder of PYnative.com. As a Python developer, I enjoy assisting students, developers, and learners. Follow me on Twitter .

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10 Python Practice Exercises for Beginners with Solutions

python basics
get started with python
online practice

A great way to improve quickly at programming with Python is to practice with a wide range of exercises and programming challenges. In this article, we give you 10 Python practice exercises to boost your skills.

Practice exercises are a great way to learn Python. Well-designed exercises expose you to new concepts, such as writing different types of loops, working with different data structures like lists, arrays, and tuples, and reading in different file types. Good exercises should be at a level that is approachable for beginners but also hard enough to challenge you, pushing your knowledge and skills to the next level.

If you’re new to Python and looking for a structured way to improve your programming, consider taking the Python Basics Practice course. It includes 17 interactive exercises designed to improve all aspects of your programming and get you into good programming habits early. Read about the course in the March 2023 episode of our series Python Course of the Month .

Take the course Python Practice: Word Games , and you gain experience working with string functions and text files through its 27 interactive exercises. Its release announcement gives you more information and a feel for how it works.

Each course has enough material to keep you busy for about 10 hours. To give you a little taste of what these courses teach you, we have selected 10 Python practice exercises straight from these courses. We’ll give you the exercises and solutions with detailed explanations about how they work.

To get the most out of this article, have a go at solving the problems before reading the solutions. Some of these practice exercises have a few possible solutions, so also try to come up with an alternative solution after you’ve gone through each exercise.

Let’s get started!

Exercise 1: User Input and Conditional Statements

Write a program that asks the user for a number then prints the following sentence that number of times: ‘I am back to check on my skills!’ If the number is greater than 10, print this sentence instead: ‘Python conditions and loops are a piece of cake.’ Assume you can only pass positive integers.

Here, we start by using the built-in function input() , which accepts user input from the keyboard. The first argument is the prompt displayed on the screen; the input is converted into an integer with int() and saved as the variable number. If the variable number is greater than 10, the first message is printed once on the screen. If not, the second message is printed in a loop number times.

Exercise 2: Lowercase and Uppercase Characters

Below is a string, text . It contains a long string of characters. Your task is to iterate over the characters of the string, count uppercase letters and lowercase letters, and print the result:

We start this one by initializing the two counters for uppercase and lowercase characters. Then, we loop through every letter in text and check if it is lowercase. If so, we increment the lowercase counter by one. If not, we check if it is uppercase and if so, we increment the uppercase counter by one. Finally, we print the results in the required format.

Exercise 3: Building Triangles

Create a function named is_triangle_possible() that accepts three positive numbers. It should return True if it is possible to create a triangle from line segments of given lengths and False otherwise. With 3 numbers, it is sometimes, but not always, possible to create a triangle: You cannot create a triangle from a = 13, b = 2, and c = 3, but you can from a = 13, b = 9, and c = 10.

The key to solving this problem is to determine when three lines make a triangle regardless of the type of triangle. It may be helpful to start drawing triangles before you start coding anything.

Notice that the sum of any two sides must be larger than the third side to form a triangle. That means we need a + b > c, c + b > a, and a + c > b. All three conditions must be met to form a triangle; hence we need the and condition in the solution. Once you have this insight, the solution is easy!

Exercise 4: Call a Function From Another Function

Create two functions: print_five_times() and speak() . The function print_five_times() should accept one parameter (called sentence) and print it five times. The function speak(sentence, repeat) should have two parameters: sentence (a string of letters), and repeat (a Boolean with a default value set to False ). If the repeat parameter is set to False , the function should just print a sentence once. If the repeat parameter is set to True, the function should call the print_five_times() function.

This is a good example of calling a function in another function. It is something you’ll do often in your programming career. It is also a nice demonstration of how to use a Boolean flag to control the flow of your program.

If the repeat parameter is True, the print_five_times() function is called, which prints the sentence parameter 5 times in a loop. Otherwise, the sentence parameter is just printed once. Note that in Python, writing if repeat is equivalent to if repeat == True .

Exercise 5: Looping and Conditional Statements

Write a function called find_greater_than() that takes two parameters: a list of numbers and an integer threshold. The function should create a new list containing all numbers in the input list greater than the given threshold. The order of numbers in the result list should be the same as in the input list. For example:

Here, we start by defining an empty list to store our results. Then, we loop through all elements in the input list and test if the element is greater than the threshold. If so, we append the element to the new list.

Notice that we do not explicitly need an else and pass to do nothing when integer is not greater than threshold . You may include this if you like.

Exercise 6: Nested Loops and Conditional Statements

Write a function called find_censored_words() that accepts a list of strings and a list of special characters as its arguments, and prints all censored words from it one by one in separate lines. A word is considered censored if it has at least one character from the special_chars list. Use the word_list variable to test your function. We've prepared the two lists for you:

This is another nice example of looping through a list and testing a condition. We start by looping through every word in word_list . Then, we loop through every character in the current word and check if the current character is in the special_chars list.

This time, however, we have a break statement. This exits the inner loop as soon as we detect one special character since it does not matter if we have one or several special characters in the word.

Exercise 7: Lists and Tuples

Create a function find_short_long_word(words_list) . The function should return a tuple of the shortest word in the list and the longest word in the list (in that order). If there are multiple words that qualify as the shortest word, return the first shortest word in the list. And if there are multiple words that qualify as the longest word, return the last longest word in the list. For example, for the following list:

the function should return

Assume the input list is non-empty.

The key to this problem is to start with a “guess” for the shortest and longest words. We do this by creating variables shortest_word and longest_word and setting both to be the first word in the input list.

We loop through the words in the input list and check if the current word is shorter than our initial “guess.” If so, we update the shortest_word variable. If not, we check to see if it is longer than or equal to our initial “guess” for the longest word, and if so, we update the longest_word variable. Having the >= condition ensures the longest word is the last longest word. Finally, we return the shortest and longest words in a tuple.

Exercise 8: Dictionaries

As you see, we've prepared the test_results variable for you. Your task is to iterate over the values of the dictionary and print all names of people who received less than 45 points.

Here, we have an example of how to iterate through a dictionary. Dictionaries are useful data structures that allow you to create a key (the names of the students) and attach a value to it (their test results). Dictionaries have the dictionary.items() method, which returns an object with each key:value pair in a tuple.

The solution shows how to loop through this object and assign a key and a value to two variables. Then, we test whether the value variable is greater than 45. If so, we print the key variable.

Exercise 9: More Dictionaries

Write a function called consonant_vowels_count(frequencies_dictionary, vowels) that takes a dictionary and a list of vowels as arguments. The keys of the dictionary are letters and the values are their frequencies. The function should print the total number of consonants and the total number of vowels in the following format:

For example, for input:

the output should be:

Working with dictionaries is an important skill. So, here’s another exercise that requires you to iterate through dictionary items.

We start by defining a list of vowels. Next, we need to define two counters, one for vowels and one for consonants, both set to zero. Then, we iterate through the input dictionary items and test whether the key is in the vowels list. If so, we increase the vowels counter by one, if not, we increase the consonants counter by one. Finally, we print out the results in the required format.

Exercise 10: String Encryption

Implement the Caesar cipher . This is a simple encryption technique that substitutes every letter in a word with another letter from some fixed number of positions down the alphabet.

For example, consider the string 'word' . If we shift every letter down one position in the alphabet, we have 'xpse' . Shifting by 2 positions gives the string 'yqtf' . Start by defining a string with every letter in the alphabet:

Name your function cipher(word, shift) , which accepts a string to encrypt, and an integer number of positions in the alphabet by which to shift every letter.

This exercise is taken from the Word Games course. We have our string containing all lowercase letters, from which we create a shifted alphabet using a clever little string-slicing technique. Next, we create an empty string to store our encrypted word. Then, we loop through every letter in the word and find its index, or position, in the alphabet. Using this index, we get the corresponding shifted letter from the shifted alphabet string. This letter is added to the end of the new_word string.

This is just one approach to solving this problem, and it only works for lowercase words. Try inputting a word with an uppercase letter; you’ll get a ValueError . When you take the Word Games course, you slowly work up to a better solution step-by-step. This better solution takes advantage of two built-in functions chr() and ord() to make it simpler and more robust. The course contains three similar games, with each game comprising several practice exercises to build up your knowledge.

Do You Want More Python Practice Exercises?

We have given you a taste of the Python practice exercises available in two of our courses, Python Basics Practice and Python Practice: Word Games . These courses are designed to develop skills important to a successful Python programmer, and the exercises above were taken directly from the courses. Sign up for our platform (it’s free!) to find more exercises like these.

We’ve discussed Different Ways to Practice Python in the past, and doing interactive exercises is just one way. Our other tips include reading books, watching videos, and taking on projects. For tips on good books for Python, check out “ The 5 Best Python Books for Beginners .” It’s important to get the basics down first and make sure your practice exercises are fun, as we discuss in “ What’s the Best Way to Practice Python? ” If you keep up with your practice exercises, you’ll become a Python master in no time!