The Simplest Way to Understand The Difference Between For Loops and While Loops

Imagine you’re a baker for a second, baking some muffins (chocolate chip, anyone?).

You’re tasked with making 12 muffins, so you’ll pour batter into 12 muffin cups in the tin. In this scenario, you have a set amount (this is important) of muffins to create.

A few days later, you’re told to make as many muffins as possible using the same batter. You re-create the same batter, but now you have to go until run out of batter - you don’t know how many (also important) muffins you’ll get out of it.

The first scenario where you’re making 12 muffins regardless if batter is leftover or not is representative of a for loop, where you know how many muffin you’re making.

The second scenario where you go until the batter is empty no matter how many muffins you make is representative of a while loop in programming looks like.

Example of a For Loop

In Python, if we know the number of times we’ll loop over something, we’ll use a for loop. This “number of times” can be a list, a range, a set, a dictionary - better generalized as an iterable. Using our example from above:

# We KNOW we're making 12 muffins
for cup_number in range(12):
    print(f"Filling muffin cup {cup_number + 1}")

Here, it doesn’t matter if there’s leftover batter, as the objective is to fill all 12 cups.

Example of a While Loop

On the contrary, if we want to go until a condition is met, we’ll use a while loop. In our example, we didn’t care about the number of muffins we made - we only cared if the batter was used entirely. In Python, this may look like this:

batter_left = 100  # Assume 100 is the total batter amount
muffin_count = 0

# Assume each muffin takes 8 units of batter
while batter_left >= 8:
    muffin_count += 1
    batter_left -= 8  # Reduce batter after each muffin
    print(f"Made muffin {muffin_count}, batter left: {batter_left}")

Hope this helps!

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