Pythonic shortcut for doubly nested for loops?

Question

Consider if I had a function that took a tuple argument (x,y), where x was in the range(X), and y in the range(Y), the normal way of doing it would be:

for x in range(X):
    for y in range(Y):
        function(x,y)

is there a way to do

for xy in something_like_range(X,Y):
    function(xy)

such that xy was a tuple (x,y)?

score 19 · Accepted Answer · answered Mar 28 '11 at 16:29

You can use product from itertools

>>> from itertools import product
>>> 
>>> for x,y in product(range(3), range(4)):
...   print (x,y)
... 
(0, 0)
(0, 1)
(0, 2)
(0, 3)
(1, 0)
(1, 1)
(1, 2)
(1, 3)

... and so on

Your code would look like:

for x,y in product(range(X), range(Y)):
    function(x,y)

score 5 · Answer 2 · answered Mar 28 '11 at 16:26

5

You can use itertools.product():

from itertools import product
for xy in product(range(X), range(Y)):
    function(xy)

answered Mar 28 '11 at 16:26

Sven Marnach

574,206
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don't need a comma b/w x and y? – yishairasowsky Oct 20 '21 at 12:49
@yishairasowsky The code works as written. `xy` will be a pair (tuple with two elements) containing one value from `X` and one from `Y` in each iteration. You can unpack the tuple by using `x, y` as the loop variable if you want to. I used `xy` as a single value here because this is what the OP asked for. – Sven Marnach Oct 20 '21 at 15:09

N 1.1 · Answer 3 · 2011-03-28T17:39:56.817

4

Pythonic they are -> (modify according to your requirements)

>>> [ (x,y)   for x in range(2)   for y in range(2)]
[(0, 0), (0, 1), (1, 0), (1, 1)]

Generator version :

gen = ( (x,y)   for x in range(2)   for y in range(2) )
>>> for x,y in gen:
...     print x,y
... 
0 0
0 1
1 0
1 1

edited Mar 28 '11 at 17:39

answered Mar 28 '11 at 16:35

N 1.1

12,418
6
43
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score 2 · Answer 4 · answered Mar 28 '11 at 16:27

2

Try product from itertools: http://docs.python.org/library/itertools.html#itertools.product

from itertools import product

for x, y in product(range(X), range(Y)):
    function(x, y)

answered Mar 28 '11 at 16:27

gruszczy

40,948
31
128
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score 0 · Answer 5 · answered Jan 18 '12 at 07:29

0

from itertools import product

def something_like_range(*sizes):
    return product(*[range(size) for size in sizes])

for a usage close to what you wanted:

for x,y in something_like_range(X,Y):
    your_function(x,y)

=)

answered Jan 18 '12 at 07:29

rakslice

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Pythonic shortcut for doubly nested for loops?

5 Answers5

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