Python If Statement - chrisbitm/python GitHub Wiki

An if statement in Python is a control flow structure that lets you execute a block of code only if a specific condition is true. It's how Python makes decisions.

Simple If Statement

age = 18

if age >= 18:
    print("You are an adult.")
  • The Code Block check if age is Greater Than OR Equal to 18. Since it is, Console will output You are an adult.

However, if you had a value that didn't evaluate a true condition. A simple IF Block won't run.

age = 15

# Won't run if Age is less than 18
if age >= 18:
    print("You are an adult.")

If-Else Statement

An If-Else lets you execute a block of code if regardless if a condition is True or False.

age = 15

if age >= 18:
    print("You are an adult.")
else:
   print("You are a minor")

If-Elif-Else Statement

An If-Elif-Else lets you execute a block of code that checks various conditions. You can have as many as you want, but for simplicity, it may not be wise. The else statement executes.

score = 75

if score >= 90:
    print("Excellent!")
elif score >= 75:
    print("Good job.")
elif score >= 60:
    print("You passed.")
else:
    print("You failed.")

Nested If Statement

A nested if statement in Python is an If Statement placed inside another If statement.

age = 20
has_id = True

if age >= 18:
    if has_id:
        print("Access granted.")
    else:
        print("ID required.")
else:
    print("Access denied. You must be 18 or older.")
  • age is Greater Than OR Equal to 18, so the first statement executes.
  • has_id is True and thus Access is granted.