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# How does python know what "number (or 'num')" is when writing a loop?

For example:

```numbers = [1, 2, 3, 4]
doubles = []
for number in numbers:
doubles.append(number*2)
```

I don't get how python understands what "number" is in this. How does python interpret this code to understand that you are referring to the numbers within the list?

Ugh that confused me for so long! In other languages. Disclaimer, I haven't glanced at python in ages, but I'm pretty sure the following is true. Someone correct me if I'm wrong.

It's just a variable, you don't have to call it "number". It might be easier to understand if you call it something completely different just to illustrate a point.

```numbers = [1,2,3,4]
doubles = []
for myVariable in numbers:
doubles.append(myVariable * 2)
```

So it just loops through the array, and with every iteration, it assigns myVariable to the value of that item in the array. It's practically doing this automatically

```myVariable = 1
doubles.append(myVariable * 2)

myVariable = 2
doubles.append(myVariable * 2)

myVariable = 3
doubles.append(myVariable * 2)

myVariable = 4
doubles.append(myVariable * 2)
```

Python understand what `number` is because the `for` loop creates it. The way a for loop works is that each time it runs it pulls out an item from a list you specify and assigns it within the loop to a variable you specify.
So `for number in numbers` is a loop that says take the items from a list called `numbers`, and pull them out one by one and assign them to the variable `number`.
The first time the loop runs your code `number` will contain the first item of `numbers`, the second time the loop runs it will contain the second item of `numbers` and so on, until it has run though all of the items.