> ## Documentation Index
> Fetch the complete documentation index at: https://docs.sourcery.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Use `itertools.product`

#### Sourcery refactoring id: `use-itertools-product`

#### Description

Replaces a nested `for` loop over independent iterables with
[`itertools.product`](https://docs.python.org/3/library/itertools.html#itertools.product).
This refactoring won't be activated if either iterable is a literal such as a
list, tuple, or set.

#### Before

```python
width = 600
height = 400

i_max, j_max = (0, 0)
for i in range(width):
    for j in range(height):
        if pixels[i, j] > pixels[i_max, j_max]:
            i_max, j_max = i, j
```

#### After

```python

width = 600
height = 400

i_max, j_max = (0, 0)
for i, j in itertools.product(range(width), range(height)):
    if pixels[i, j] > pixels[i_max, j_max]:
        i_max, j_max = i, j
```

#### Explanation

The itertools product simplifies repeated for loops into a single iterator. This
shortens the code, removes one level of nesting, collects together related
variables (facilitating refactoring), and has better semantics (c.f.
[Cartesian product](https://en.wikipedia.org/wiki/Cartesian_product)) in a
number of applications (such as grid operations as in the example above).

See also:
[`itertools.combinations`](https://docs.python.org/3/library/itertools.html#itertools.combinations)