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Menu iconMenu iconPython Programming Unlocked for Beginners
Python Programming Unlocked for Beginners
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Chapter 4: Control Structures
4.1: Conditional Statements (if, elif, else)
4.2: Loops (for, while)
4.3: Loop Control (break, continue)
4.4: Nested Control Structures
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Chapter 4: Control Structures

4.1: Conditional Statements (if, elif, else)

In this chapter, we will delve into the numerous control structures available in Python, which allow you to create more complex and dynamic programs. Control structures are the backbone of any programming language, as they enable you to control the flow of your program's execution based on conditions or loops. 

First, we will cover conditional statements, which allow your program to make decisions based on certain conditions. These statements include if, elif, and else statements, which are used to execute different blocks of code depending on the outcome of the condition.

Next, we will move on to loops, which are used to execute a block of code repeatedly. There are two main types of loops in Python: for loops and while loops. For loops are used to iterate over a sequence of elements, while loops are used to execute a block of code repeatedly as long as a certain condition is true. 

Finally, we will explore the use of break and continue statements, which allow you to modify the behavior of your loops. The break statement is used to exit a loop prematurely, while the continue statement is used to skip over certain iterations of a loop.

Overall, understanding control structures is essential for any Python programmer looking to create more advanced programs, and this chapter will equip you with the knowledge needed to do just that.

In Python, conditional statements are used to make decisions based on certain conditions. These statements help you to control the flow of your program, allowing it to react differently depending on the input or the current state of your data. The primary conditional statements in Python are if, elif, and else. 

The if statement is used to test a condition. If the condition is true, the code block following the if statement will be executed. The general syntax of an if statement is as follows:

if condition:
    # Code to be executed if the condition is true

For example, let's say we want to check if a number is positive:

number = 5

if number > 0:
    print("The number is positive.")

The elif (short for "else if") statement is used when you want to test multiple conditions. It is placed after an if statement and is executed only if the previous conditions were false. The general syntax of an elif statement is as follows:

if condition1:
    # Code to be executed if condition1 is true
elif condition2:
    # Code to be executed if condition1 is false and condition2 is true

For example, let's say we want to check if a number is positive, negative, or zero:

number = 0

if number > 0:
    print("The number is positive.")
elif number < 0:
    print("The number is negative.")

The else statement is used to execute code when none of the previous conditions are met (i.e., they are all false). It is placed after the if and/or elif statements. The general syntax of an else statement is as follows:

if condition1:
    # Code to be executed if condition1 is true
elif condition2:
    # Code to be executed if condition1 is false and condition2 is true
else:
    # Code to be executed if all conditions are false

Continuing with the previous example, let's add an else statement to handle the case when the number is zero:

number = 0

if number > 0:
    print("The number is positive.")
elif number < 0:
    print("The number is negative.")
else:
    print("The number is zero.")

In summary, conditional statements in Python are a fundamental programming concept that allow you to control the flow of your program based on specific conditions. By using if, elif, and else statements, you can execute different code blocks depending on the given conditions. This is a powerful tool that you can use to create complex programs with dynamic behavior.

Moreover, mastering control structures is essential for any programmer. Beyond conditional statements, loops are another important control structure that you will encounter frequently. With loops, you can iterate through a set of instructions repeatedly until a certain condition is met. This can be useful for tasks such as data processing or user input validation.

Another advanced control structure is the use of break and continue statements. These statements allow you to modify the behavior of loops based on certain conditions. For example, you can use a break statement to terminate a loop early if a specific condition is met. On the other hand, a continue statement can be used to skip over a certain iteration of the loop if a condition is met.

In the following topics, we will discuss these and other control structures in more detail, so that you can become a more proficient Python programmer.

Exercise 4.1.1: Odd or Even Number

In this exercise, you will write a Python program that determines if a given number is odd or even. You will practice using if and else statements.

Instructions:

  1. Create a new Python file or open a Python interpreter.
  2. Assign an integer value to a variable named number.
  3. Use an if statement to check if the number is even (i.e., divisible by 2) and print a message indicating that it's an even number.
  4. Use an else statement to handle the case where the number is odd and print a message indicating that it's an odd number.

Your final code should look something like this:

number = 7

if number % 2 == 0:
    print(f"{number} is an even number.")
else:
    print(f"{number} is an odd number.")

Output example:

7 is an odd number.

Exercise 4.1.2: Age Group Classification

In this exercise, you will write a Python program that classifies a person's age group based on their age. You will practice using if, elif, and else statements.

Instructions:

  1. Create a new Python file or open a Python interpreter.
  2. Assign an integer value to a variable named age.
  3. Use if, elif, and else statements to classify the age group as "Child" (0-12), "Teenager" (13-19), "Adult" (20-59), or "Senior" (60 and above), and print the corresponding classification.

Your final code should look something like this:

age = 25

if age >= 0 and age <= 12:
    print("Child")
elif age >= 13 and age <= 19:
    print("Teenager")
elif age >= 20 and age <= 59:
    print("Adult")
else:
    print("Senior")

Output example:

Adult

Exercise 4.1.3: Letter Grade Calculation

In this exercise, you will write a Python program that assigns a letter grade based on a student's test score. You will practice using if, elif, and else statements.

Instructions:

  1. Create a new Python file or open a Python interpreter.
  2. Assign an integer value (0-100) to a variable named score.
  3. Use if, elif, and else statements to assign a letter grade (A, B, C, D, or F) based on the score, and print the corresponding letter grade.

The grading scale is as follows:

  • A: 90-100
  • B: 80-89
  • C: 70-79
  • D: 60-69
  • F: 0-59

Your final code should look something like this:

score = 85

if score >= 90 and score <= 100:
    print("A")
elif score >= 80 and score < 90:
    print("B")
elif score >= 70 and score < 80:
    print("C")
elif score >= 60 and score < 70:
    print("D")
else:
    print("F")

Output example:

B

These exercises help you become familiar with using conditional statements in Python to control the flow of your programs.

4.1: Conditional Statements (if, elif, else)

In this chapter, we will delve into the numerous control structures available in Python, which allow you to create more complex and dynamic programs. Control structures are the backbone of any programming language, as they enable you to control the flow of your program's execution based on conditions or loops. 

First, we will cover conditional statements, which allow your program to make decisions based on certain conditions. These statements include if, elif, and else statements, which are used to execute different blocks of code depending on the outcome of the condition.

Next, we will move on to loops, which are used to execute a block of code repeatedly. There are two main types of loops in Python: for loops and while loops. For loops are used to iterate over a sequence of elements, while loops are used to execute a block of code repeatedly as long as a certain condition is true. 

Finally, we will explore the use of break and continue statements, which allow you to modify the behavior of your loops. The break statement is used to exit a loop prematurely, while the continue statement is used to skip over certain iterations of a loop.

Overall, understanding control structures is essential for any Python programmer looking to create more advanced programs, and this chapter will equip you with the knowledge needed to do just that.

In Python, conditional statements are used to make decisions based on certain conditions. These statements help you to control the flow of your program, allowing it to react differently depending on the input or the current state of your data. The primary conditional statements in Python are if, elif, and else. 

The if statement is used to test a condition. If the condition is true, the code block following the if statement will be executed. The general syntax of an if statement is as follows:

if condition:
    # Code to be executed if the condition is true

For example, let's say we want to check if a number is positive:

number = 5

if number > 0:
    print("The number is positive.")

The elif (short for "else if") statement is used when you want to test multiple conditions. It is placed after an if statement and is executed only if the previous conditions were false. The general syntax of an elif statement is as follows:

if condition1:
    # Code to be executed if condition1 is true
elif condition2:
    # Code to be executed if condition1 is false and condition2 is true

For example, let's say we want to check if a number is positive, negative, or zero:

number = 0

if number > 0:
    print("The number is positive.")
elif number < 0:
    print("The number is negative.")

The else statement is used to execute code when none of the previous conditions are met (i.e., they are all false). It is placed after the if and/or elif statements. The general syntax of an else statement is as follows:

if condition1:
    # Code to be executed if condition1 is true
elif condition2:
    # Code to be executed if condition1 is false and condition2 is true
else:
    # Code to be executed if all conditions are false

Continuing with the previous example, let's add an else statement to handle the case when the number is zero:

number = 0

if number > 0:
    print("The number is positive.")
elif number < 0:
    print("The number is negative.")
else:
    print("The number is zero.")

In summary, conditional statements in Python are a fundamental programming concept that allow you to control the flow of your program based on specific conditions. By using if, elif, and else statements, you can execute different code blocks depending on the given conditions. This is a powerful tool that you can use to create complex programs with dynamic behavior.

Moreover, mastering control structures is essential for any programmer. Beyond conditional statements, loops are another important control structure that you will encounter frequently. With loops, you can iterate through a set of instructions repeatedly until a certain condition is met. This can be useful for tasks such as data processing or user input validation.

Another advanced control structure is the use of break and continue statements. These statements allow you to modify the behavior of loops based on certain conditions. For example, you can use a break statement to terminate a loop early if a specific condition is met. On the other hand, a continue statement can be used to skip over a certain iteration of the loop if a condition is met.

In the following topics, we will discuss these and other control structures in more detail, so that you can become a more proficient Python programmer.

Exercise 4.1.1: Odd or Even Number

In this exercise, you will write a Python program that determines if a given number is odd or even. You will practice using if and else statements.

Instructions:

  1. Create a new Python file or open a Python interpreter.
  2. Assign an integer value to a variable named number.
  3. Use an if statement to check if the number is even (i.e., divisible by 2) and print a message indicating that it's an even number.
  4. Use an else statement to handle the case where the number is odd and print a message indicating that it's an odd number.

Your final code should look something like this:

number = 7

if number % 2 == 0:
    print(f"{number} is an even number.")
else:
    print(f"{number} is an odd number.")

Output example:

7 is an odd number.

Exercise 4.1.2: Age Group Classification

In this exercise, you will write a Python program that classifies a person's age group based on their age. You will practice using if, elif, and else statements.

Instructions:

  1. Create a new Python file or open a Python interpreter.
  2. Assign an integer value to a variable named age.
  3. Use if, elif, and else statements to classify the age group as "Child" (0-12), "Teenager" (13-19), "Adult" (20-59), or "Senior" (60 and above), and print the corresponding classification.

Your final code should look something like this:

age = 25

if age >= 0 and age <= 12:
    print("Child")
elif age >= 13 and age <= 19:
    print("Teenager")
elif age >= 20 and age <= 59:
    print("Adult")
else:
    print("Senior")

Output example:

Adult

Exercise 4.1.3: Letter Grade Calculation

In this exercise, you will write a Python program that assigns a letter grade based on a student's test score. You will practice using if, elif, and else statements.

Instructions:

  1. Create a new Python file or open a Python interpreter.
  2. Assign an integer value (0-100) to a variable named score.
  3. Use if, elif, and else statements to assign a letter grade (A, B, C, D, or F) based on the score, and print the corresponding letter grade.

The grading scale is as follows:

  • A: 90-100
  • B: 80-89
  • C: 70-79
  • D: 60-69
  • F: 0-59

Your final code should look something like this:

score = 85

if score >= 90 and score <= 100:
    print("A")
elif score >= 80 and score < 90:
    print("B")
elif score >= 70 and score < 80:
    print("C")
elif score >= 60 and score < 70:
    print("D")
else:
    print("F")

Output example:

B

These exercises help you become familiar with using conditional statements in Python to control the flow of your programs.

4.1: Conditional Statements (if, elif, else)

In this chapter, we will delve into the numerous control structures available in Python, which allow you to create more complex and dynamic programs. Control structures are the backbone of any programming language, as they enable you to control the flow of your program's execution based on conditions or loops. 

First, we will cover conditional statements, which allow your program to make decisions based on certain conditions. These statements include if, elif, and else statements, which are used to execute different blocks of code depending on the outcome of the condition.

Next, we will move on to loops, which are used to execute a block of code repeatedly. There are two main types of loops in Python: for loops and while loops. For loops are used to iterate over a sequence of elements, while loops are used to execute a block of code repeatedly as long as a certain condition is true. 

Finally, we will explore the use of break and continue statements, which allow you to modify the behavior of your loops. The break statement is used to exit a loop prematurely, while the continue statement is used to skip over certain iterations of a loop.

Overall, understanding control structures is essential for any Python programmer looking to create more advanced programs, and this chapter will equip you with the knowledge needed to do just that.

In Python, conditional statements are used to make decisions based on certain conditions. These statements help you to control the flow of your program, allowing it to react differently depending on the input or the current state of your data. The primary conditional statements in Python are if, elif, and else. 

The if statement is used to test a condition. If the condition is true, the code block following the if statement will be executed. The general syntax of an if statement is as follows:

if condition:
    # Code to be executed if the condition is true

For example, let's say we want to check if a number is positive:

number = 5

if number > 0:
    print("The number is positive.")

The elif (short for "else if") statement is used when you want to test multiple conditions. It is placed after an if statement and is executed only if the previous conditions were false. The general syntax of an elif statement is as follows:

if condition1:
    # Code to be executed if condition1 is true
elif condition2:
    # Code to be executed if condition1 is false and condition2 is true

For example, let's say we want to check if a number is positive, negative, or zero:

number = 0

if number > 0:
    print("The number is positive.")
elif number < 0:
    print("The number is negative.")

The else statement is used to execute code when none of the previous conditions are met (i.e., they are all false). It is placed after the if and/or elif statements. The general syntax of an else statement is as follows:

if condition1:
    # Code to be executed if condition1 is true
elif condition2:
    # Code to be executed if condition1 is false and condition2 is true
else:
    # Code to be executed if all conditions are false

Continuing with the previous example, let's add an else statement to handle the case when the number is zero:

number = 0

if number > 0:
    print("The number is positive.")
elif number < 0:
    print("The number is negative.")
else:
    print("The number is zero.")

In summary, conditional statements in Python are a fundamental programming concept that allow you to control the flow of your program based on specific conditions. By using if, elif, and else statements, you can execute different code blocks depending on the given conditions. This is a powerful tool that you can use to create complex programs with dynamic behavior.

Moreover, mastering control structures is essential for any programmer. Beyond conditional statements, loops are another important control structure that you will encounter frequently. With loops, you can iterate through a set of instructions repeatedly until a certain condition is met. This can be useful for tasks such as data processing or user input validation.

Another advanced control structure is the use of break and continue statements. These statements allow you to modify the behavior of loops based on certain conditions. For example, you can use a break statement to terminate a loop early if a specific condition is met. On the other hand, a continue statement can be used to skip over a certain iteration of the loop if a condition is met.

In the following topics, we will discuss these and other control structures in more detail, so that you can become a more proficient Python programmer.

Exercise 4.1.1: Odd or Even Number

In this exercise, you will write a Python program that determines if a given number is odd or even. You will practice using if and else statements.

Instructions:

  1. Create a new Python file or open a Python interpreter.
  2. Assign an integer value to a variable named number.
  3. Use an if statement to check if the number is even (i.e., divisible by 2) and print a message indicating that it's an even number.
  4. Use an else statement to handle the case where the number is odd and print a message indicating that it's an odd number.

Your final code should look something like this:

number = 7

if number % 2 == 0:
    print(f"{number} is an even number.")
else:
    print(f"{number} is an odd number.")

Output example:

7 is an odd number.

Exercise 4.1.2: Age Group Classification

In this exercise, you will write a Python program that classifies a person's age group based on their age. You will practice using if, elif, and else statements.

Instructions:

  1. Create a new Python file or open a Python interpreter.
  2. Assign an integer value to a variable named age.
  3. Use if, elif, and else statements to classify the age group as "Child" (0-12), "Teenager" (13-19), "Adult" (20-59), or "Senior" (60 and above), and print the corresponding classification.

Your final code should look something like this:

age = 25

if age >= 0 and age <= 12:
    print("Child")
elif age >= 13 and age <= 19:
    print("Teenager")
elif age >= 20 and age <= 59:
    print("Adult")
else:
    print("Senior")

Output example:

Adult

Exercise 4.1.3: Letter Grade Calculation

In this exercise, you will write a Python program that assigns a letter grade based on a student's test score. You will practice using if, elif, and else statements.

Instructions:

  1. Create a new Python file or open a Python interpreter.
  2. Assign an integer value (0-100) to a variable named score.
  3. Use if, elif, and else statements to assign a letter grade (A, B, C, D, or F) based on the score, and print the corresponding letter grade.

The grading scale is as follows:

  • A: 90-100
  • B: 80-89
  • C: 70-79
  • D: 60-69
  • F: 0-59

Your final code should look something like this:

score = 85

if score >= 90 and score <= 100:
    print("A")
elif score >= 80 and score < 90:
    print("B")
elif score >= 70 and score < 80:
    print("C")
elif score >= 60 and score < 70:
    print("D")
else:
    print("F")

Output example:

B

These exercises help you become familiar with using conditional statements in Python to control the flow of your programs.

4.1: Conditional Statements (if, elif, else)

In this chapter, we will delve into the numerous control structures available in Python, which allow you to create more complex and dynamic programs. Control structures are the backbone of any programming language, as they enable you to control the flow of your program's execution based on conditions or loops. 

First, we will cover conditional statements, which allow your program to make decisions based on certain conditions. These statements include if, elif, and else statements, which are used to execute different blocks of code depending on the outcome of the condition.

Next, we will move on to loops, which are used to execute a block of code repeatedly. There are two main types of loops in Python: for loops and while loops. For loops are used to iterate over a sequence of elements, while loops are used to execute a block of code repeatedly as long as a certain condition is true. 

Finally, we will explore the use of break and continue statements, which allow you to modify the behavior of your loops. The break statement is used to exit a loop prematurely, while the continue statement is used to skip over certain iterations of a loop.

Overall, understanding control structures is essential for any Python programmer looking to create more advanced programs, and this chapter will equip you with the knowledge needed to do just that.

In Python, conditional statements are used to make decisions based on certain conditions. These statements help you to control the flow of your program, allowing it to react differently depending on the input or the current state of your data. The primary conditional statements in Python are if, elif, and else. 

The if statement is used to test a condition. If the condition is true, the code block following the if statement will be executed. The general syntax of an if statement is as follows:

if condition:
    # Code to be executed if the condition is true

For example, let's say we want to check if a number is positive:

number = 5

if number > 0:
    print("The number is positive.")

The elif (short for "else if") statement is used when you want to test multiple conditions. It is placed after an if statement and is executed only if the previous conditions were false. The general syntax of an elif statement is as follows:

if condition1:
    # Code to be executed if condition1 is true
elif condition2:
    # Code to be executed if condition1 is false and condition2 is true

For example, let's say we want to check if a number is positive, negative, or zero:

number = 0

if number > 0:
    print("The number is positive.")
elif number < 0:
    print("The number is negative.")

The else statement is used to execute code when none of the previous conditions are met (i.e., they are all false). It is placed after the if and/or elif statements. The general syntax of an else statement is as follows:

if condition1:
    # Code to be executed if condition1 is true
elif condition2:
    # Code to be executed if condition1 is false and condition2 is true
else:
    # Code to be executed if all conditions are false

Continuing with the previous example, let's add an else statement to handle the case when the number is zero:

number = 0

if number > 0:
    print("The number is positive.")
elif number < 0:
    print("The number is negative.")
else:
    print("The number is zero.")

In summary, conditional statements in Python are a fundamental programming concept that allow you to control the flow of your program based on specific conditions. By using if, elif, and else statements, you can execute different code blocks depending on the given conditions. This is a powerful tool that you can use to create complex programs with dynamic behavior.

Moreover, mastering control structures is essential for any programmer. Beyond conditional statements, loops are another important control structure that you will encounter frequently. With loops, you can iterate through a set of instructions repeatedly until a certain condition is met. This can be useful for tasks such as data processing or user input validation.

Another advanced control structure is the use of break and continue statements. These statements allow you to modify the behavior of loops based on certain conditions. For example, you can use a break statement to terminate a loop early if a specific condition is met. On the other hand, a continue statement can be used to skip over a certain iteration of the loop if a condition is met.

In the following topics, we will discuss these and other control structures in more detail, so that you can become a more proficient Python programmer.

Exercise 4.1.1: Odd or Even Number

In this exercise, you will write a Python program that determines if a given number is odd or even. You will practice using if and else statements.

Instructions:

  1. Create a new Python file or open a Python interpreter.
  2. Assign an integer value to a variable named number.
  3. Use an if statement to check if the number is even (i.e., divisible by 2) and print a message indicating that it's an even number.
  4. Use an else statement to handle the case where the number is odd and print a message indicating that it's an odd number.

Your final code should look something like this:

number = 7

if number % 2 == 0:
    print(f"{number} is an even number.")
else:
    print(f"{number} is an odd number.")

Output example:

7 is an odd number.

Exercise 4.1.2: Age Group Classification

In this exercise, you will write a Python program that classifies a person's age group based on their age. You will practice using if, elif, and else statements.

Instructions:

  1. Create a new Python file or open a Python interpreter.
  2. Assign an integer value to a variable named age.
  3. Use if, elif, and else statements to classify the age group as "Child" (0-12), "Teenager" (13-19), "Adult" (20-59), or "Senior" (60 and above), and print the corresponding classification.

Your final code should look something like this:

age = 25

if age >= 0 and age <= 12:
    print("Child")
elif age >= 13 and age <= 19:
    print("Teenager")
elif age >= 20 and age <= 59:
    print("Adult")
else:
    print("Senior")

Output example:

Adult

Exercise 4.1.3: Letter Grade Calculation

In this exercise, you will write a Python program that assigns a letter grade based on a student's test score. You will practice using if, elif, and else statements.

Instructions:

  1. Create a new Python file or open a Python interpreter.
  2. Assign an integer value (0-100) to a variable named score.
  3. Use if, elif, and else statements to assign a letter grade (A, B, C, D, or F) based on the score, and print the corresponding letter grade.

The grading scale is as follows:

  • A: 90-100
  • B: 80-89
  • C: 70-79
  • D: 60-69
  • F: 0-59

Your final code should look something like this:

score = 85

if score >= 90 and score <= 100:
    print("A")
elif score >= 80 and score < 90:
    print("B")
elif score >= 70 and score < 80:
    print("C")
elif score >= 60 and score < 70:
    print("D")
else:
    print("F")

Output example:

B

These exercises help you become familiar with using conditional statements in Python to control the flow of your programs.

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