Python Loops
Loops in Python are like repeating instructions in your code, saving you from writing the same lines over and over. They’re perfect for tasks like going through a list of items or counting until a goal is reached. Below, we’ll cover the main types in simple terms, with easy examples you can try yourself.
For Loop
The For Loop is used when you have a specific list of items or a set number of steps you want to complete. It’s like a delivery driver who has five packages; they will stop at each house on their route one by one until the truck is empty.
- When to use it: When you know exactly how many times you need to repeat something or when you’re moving through a collection (like a list of names).
# Printing a simple greeting for every friend in a list
friends = ["Alice", "Bob", "Charlie"]
for name in friends:
print("Hello, " + name)
While Loop
A While Loop keeps running as long as a specific rule or condition stays true. It’s like a vacuum cleaner that stays turned on as long as the power switch is in the “On” position; the moment you flip it to “Off”, the loop stops immediately.
- When to use it: When you don’t know exactly how many times you’ll need to repeat the task, but you know what condition should make it stop.
# Counting down until the battery runs out
battery = 3
while battery > 0:
print("Phone is on...")
battery = battery - 1 # Reducing battery by 1 each time
print("Phone shut down.")
Nested Loops
A Nested Loop is simply a loop placed inside another loop. Think of it like a clock: the “hour” hand moves once (the outer loop), but before it can move again, the “minute” hand must go all the way around 60 times (the inner loop).
- When to use it: When you have complex data, like a grid of numbers or a schedule with multiple days and multiple tasks per day.
# Matching every shirt color with every pant color
shirts = ["Red", "Blue"]
pants = ["Jeans", "Slacks"]
for s in shirts:
for p in pants:
print(s + " shirt with " + p)