# What Does the “yield” Keyword Do in Python?

To better understand what `yield` does, you need first to understand what `generator` and `iterable` are.

## What is `iterable`

When you use a list or list-like structure, you can read the values from the list one by one. This is called iteration. 

```python
list_of_numbers = [1,10,100,1000]

# iterating over the list
for i in list_of_numbers:
	print(i)
```

This is why in many languages, the iterating variable is usually named `i`, but it can be named however you like. In short, basically, anything that can be used in `for _ in _` is iterable.

## What is `generator`

Generators are special kinds of iterables. They don’t store the values in memory, but rather generate the value on the fly. This means you can only iterate over them once.

```python
generator = (x + 1 for x in range(4))

for i in generator:
	print(i)
```

## What is `yield`

Finally the `yield` keyword. `yield` is used like return but instead of returning a single value it returns a generator. This is very useful when your function will return a huge set of values that you don’t want to store in memory.

```python
def create_generator(n):
	for i in range(n):
		yield n + 1

generator = create_generator(4)

for i in generator:
	print(i)
```

In the example above, when calling the function `create_generator`, the function doesn’t return, instead, it creates a generator object.