Python 3 – Decision Making

In programming and software development, decision making is an essential part of creating functional and efficient systems. In Python, as in many programming languages, the if-else statement is one of the key tools for decision making. In this article, we will explore how decision making works in Python 3 and how you can use if-else statements to control program flow.

The if Statement

The if statement is used to execute specific code only when a certain condition is met. Here is an example of the basic syntax of an if statement in Python:

if condition:
    statement(s)

The condition is a boolean expression and the statement(s) are the code to be executed if the condition is true. Here is a simple example code that demonstrates the if statement:

x = 10

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

In this code, the condition is “x > 5”, which evaluates to true since x is 10. Therefore, the code inside the if statement is executed, which prints the message “x is greater than 5”.

The else Statement

The else statement is used with the if statement to provide an alternative set of statements when the condition is false. Here is an example of the basic syntax of an if-else statement:

if condition:
    statement(s)
else:
    statement(s)

In this code, if the condition is true, the first set of statements are executed, otherwise, the else block is executed. Here is an example code that demonstrates the if-else statement:

x = 3

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

In this code, the condition “x > 5” evaluates to false, so the code inside the else block is executed, which prints the message “x is less than or equal to 5”.

The elif Statement

The elif statement is used to test multiple conditions, and is typically used in combination with if and else statements. Here is an example of the basic syntax of an if-elif-else statement:

if condition:
    statement(s)
elif condition:
    statement(s)
else:
    statement(s)

In this code, if the first condition is true, the first set of statements are executed, otherwise, the elif block is evaluated. If the elif condition is true, the elif block is executed, otherwise, the else block is executed. Here is an example code that demonstrates the if-elif-else statement:

x = 5

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

In this code, the first condition is false, but the elif condition evaluates to true, so the code inside the elif block is executed, which prints the message “x is equal to 5”.

The Conditional Expression (Ternary Operator)

Python also has a conditional expression, also called the ternary operator, which is a shorthand way of writing an if-else statement. Here is an example of the basic syntax of a conditional expression:

value_if_true if condition else value_if_false

In this code, if the condition is true, the expression evaluates to value_if_true, otherwise, it evaluates to value_if_false. Here is an example code that demonstrates the conditional expression:

age = 20

status = "adult" if age >= 18 else "minor"

print(status)

In this code, if the age is greater than or equal to 18, the expression evaluates to “adult”, otherwise, it evaluates to “minor”, which is printed to the console.

Conclusion

Decision making is a critical part of programming, and the if-else statement is a fundamental tool for controlling program flow in Python 3. Along with the if-else statement, Python also has the elif statement and the ternary operator, which provide additional flexibility and functionality. By understanding these decision making tools, you can create more sophisticated and efficient programs in Python.