# Reduce

**Reduce** is a higher-order function that is either a built-in function in Python 2.7 or can be imported from functools in Python 3.2+.

Given a *two-argument* function, an iterable, and (optionally) an initalizer, `reduce`

applies the function to each item pair in the sequence cumulatively, and returns a single value.

`Reduce`

will take the first two elements of the iterable, apply the function to them, and reach a result. It will then apply the function to this result and the third element, move on to the fourth element, and so on, until it reaches the end of the iterable. The final result will be the single return value.

## Form

The most general form of the `reduce`

function is as follows:

reduce(func, iter)

with `func`

being the 2-argument function given, and `iter`

being the iterable being processed.

## Examples

### add_together

For the most basic example, we will attempt to add all elements of a list together. We'll create a starter function, `add_together`

, and the list `my_list`

below.

def add_together(x, y): return x+y my_list = [1, 2, 3, 4, 5]

If we apply `reduce`

to the above and apply them as arguments, we can expect:

>>>reduce(add_together, my_list) 15