Is there a Python equivalent of range(n) for multidimensional ranges?

Question

On Python, range(3) will return [0,1,2]. Is there an equivalent for multidimensional ranges?

range((3,2)) # [(0,0),(0,1),(1,0),(1,1),(2,0),(2,1)] 

So, for example, looping though the tiles of a rectangular area on a tile-based game could be written as:

for x,y in range((3,2)): 

Note I'm not asking for an implementation. I would like to know if this is a recognized pattern and if there is a built-in function on Python or it's standard/common libraries.

Answer 1

You could use itertools.product():

>>> import itertools >>> for (i,j,k) in itertools.product(xrange(3),xrange(3),xrange(3)): ...     print i,j,k 

The multiple repeated xrange() statements could be expressed like so, if you want to scale this up to a ten-dimensional loop or something similarly ridiculous:

>>> for combination in itertools.product( xrange(3), repeat=10 ): ...     print combination 

Which loops over ten variables, varying from (0,0,0,0,0,0,0,0,0,0) to (2,2,2,2,2,2,2,2,2,2).

---

In general itertools is an insanely awesome module. In the same way regexps are vastly more expressive than "plain" string methods, itertools is a very elegant way of expressing complex loops. You owe it to yourself to read the itertools module documentation. It will make your life more fun.

Answer 2

In numpy, it's numpy.ndindex. Also have a look at numpy.ndenumerate.

E.g.

import numpy as np for x, y in np.ndindex((3,2)):     print(x, y) 

This yields:

0 0 0 1 1 0 1 1 2 0 2 1