## Lists and Loops

### Video Transcript

In this section, we're going to use loops to iterate over lists. There are two main ways to loop over a list.
The first way uses the `in` keyword. `in` has two jobs: it can be used as a condition to check if a list contains some value, or it can be used to iterate over the elements of a list one at a time. This method is convenient if we just want to look at each of the elements in a list without changing them:
```numbers = [6, 8, 2, 9, 7]

print(6 in numbers) # True
print(0 in numbers) # False

for number in numbers:
print(number)
# prints 6, 8, 2, 9, 7
```
The second way uses the `len` function to get the number of elements in the list, and then `range` to loop over the numbers 0 to `len(list) - 1`, which gives the index. Because we have access to the index, we can use this method whenever we want to change the values in a list:
```numbers = [6, 8, 2, 9, 7]

for i in range(len(numbers)):
numbers[i] = numbers[i] ** 2

print(numbers)
# [36, 64, 4, 81, 49]
```