Python Basics - Control Flow Statements

Introduction to control flow statements like if, elif, and else

Control flow statements allow you to control the execution of code based on certain conditions. In Python, the primary control flow statements are if, elif, and else. These statements enable you to execute different blocks of code depending on the conditions you specify.

if Statement

The if statement is used to execute a block of code if a specified condition is true:

# Example of if statement
x = 10

if x > 5:
    print("x is greater than 5")
            

In this example, the message "x is greater than 5" will be printed because the condition x > 5 is true.

elif Statement

The elif statement stands for "else if" and allows you to check multiple conditions. If the first if statement is false, the program checks the elif condition:

# Example of elif statement
x = 10

if x > 15:
    print("x is greater than 15")
elif x > 5:
    print("x is greater than 5 but less than or equal to 15")
            

In this example, the message "x is greater than 5 but less than or equal to 15" will be printed because the condition x > 5 is true, and the if condition x > 15 is false.

else Statement

The else statement is used to execute a block of code if all preceding if and elif conditions are false:

# Example of else statement
x = 10

if x > 15:
    print("x is greater than 15")
elif x > 5:
    print("x is greater than 5 but less than or equal to 15")
else:
    print("x is 5 or less")
            

In this example, the else block will not be executed because the condition x > 5 is true.

Combining if, elif, and else Statements

You can combine if, elif, and else statements to create complex conditional logic:

# Example of combining if, elif, and else statements
x = 10

if x > 15:
    print("x is greater than 15")
elif x > 10:
    print("x is greater than 10 but less than or equal to 15")
elif x > 5:
    print("x is greater than 5 but less than or equal to 10")
else:
    print("x is 5 or less")
            

In this example, the message "x is greater than 5 but less than or equal to 10" will be printed because the condition x > 5 is true, and the preceding conditions are false.

Nesting Control Flow Statements

You can nest control flow statements to create more complex logic:

# Example of nesting control flow statements
x = 10
y = 20

if x > 5:
    if y > 15:
        print("x is greater than 5 and y is greater than 15")
    else:
        print("x is greater than 5 but y is 15 or less")
else:
    print("x is 5 or less")
            

In this example, the message "x is greater than 5 and y is greater than 15" will be printed because both conditions x > 5 and y > 15 are true.

Summary

In this tutorial, you learned about control flow statements in Python, including if, elif, and else. These statements allow you to execute different blocks of code based on specified conditions, enabling you to implement complex logic in your programs.