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Decision Making in Python

Hey there! In this guide, we'll explore decision-making in Python. Decision-making constructs allow you to execute code based on certain conditions. Let's dive in!

Decision Making​

  • Python supports several decision-making constructs that allow you to execute code based on conditions.

  • We will go over the different decision-making options available in Python.

1. If Statements​

The simplest decision-making structure in Python is the if statement, which executes a block of code if a certain condition is met.

num = 8                             # Initialize variable 'num' with a value of 8  
if num > 0:                          # Check if the value of 'num' is greater than 0  
    print('The number is positive.')  # Print a message if the condition is true

2. If-Else Statements​

The if-else statement allows you to execute one block of code if the condition is true, and another if the condition is false.

num = 11                                # Initialize variable 'num' with a value of 11  
if num % 2 == 0:                        # Check if 'num' is even  
    print('The number is even.')        # Print this message if 'num' is even  
else:                                   # Otherwise, execute this block  
    print('The number is odd.')         # Print this message if 'num' is odd

3. Else If (Elif) Statements​

The elif statement (short for else if) allows you to check multiple conditions in sequence and execute the first block of code where the condition is true.

num = 15                                  # Initialize variable 'num' with a value of 15  
if num > 20:                               # Check if 'num' is greater than 20  
    print('The number is greater than 20.') # Print this message if 'num' is greater than 20  
elif num == 15:                              # Check if 'num' is equal to 15  
    print('The number is 15.')                # Print this message if 'num' is equal to 15  
else:                                          # Otherwise, execute this block  
    print('The number is less than 20.')        # Print this message if 'num' is less than 20

4. Nested If Statements​

You can use if statements inside other if statements, known as nested if statements, to evaluate more complex conditions.

num = 7                                                 # Initialize variable 'num' with a value of 7  
if num > 0:                                               # Check if 'num' is positive  
    if num < 10:                                            # Check if 'num' is less than 10  
        print('The number is positive and less than 10.')  # Print this message if both conditions are true

5. Ternary Operator​

Python also supports a shorthand for the if-else statement, called the ternary operator.

age = 18                                # Initialize variable 'age' with a value of 18  
can_vote = 'Yes' if age >= 18 else 'No'  # Use the ternary operator to check if 'age' is 18 or older  
print(can_vote)                          # Output: 'Yes'

6. Switch Statements (Python 3.10+)​

From Python 3.10, the match-case statement is introduced, which works similarly to a switch statement in other languages.

day = 2                     # Initialize variable 'day' with a value of 2  
match day:                  # Use match-case to determine the day of the week  
    case 1:  
        print('Monday')         # Execute if 'day' is 1  
    case 2:  
        print('Tuesday')        # Execute if 'day' is 2  
    case 3:  
        print('Wednesday')      # Execute if 'day' is 3  
    case _:                     # Default case  
        print('Invalid day')    # Execute if none of the above cases match