Generating a 2-d array with iterations using Python

Question

For example I have the following 2-d array

t = [[1,2,3],
     [4,5],
     [6,7]]

by using list comprehensions i get

>>> [[x, y, z] for x in t[2] for y in t[1] for z in t[0]]
[[6, 4, 1], 
 [6, 4, 2], 
 [6, 4, 3], 
 [6, 5, 1], 
 [6, 5, 2], 
 [6, 5, 3], 
 [7, 4, 1], 
 [7, 4, 2], 
 [7, 4, 3], 
 [7, 5, 1], 
 [7, 5, 2], 
 [7, 5, 3]]

But how if the inputs has more than 3 lists? I mean, I don't want hard codes the t[2], and something like that. I want to take t consisting any number of lists as input. Is there anyway using list comprehensions to do this?

Thanks in advance!

I'd take a look at itertools

cenna75
– cenna75

2013-10-11 09:00:51 +00:00
Commented Oct 11, 2013 at 9:00 — cenna75
– cenna75, Commented Oct 11, 2013 at 9:00

falsetru · Accepted Answer · 2013-10-11 09:00:56Z

4

Use itertools.product:

>>> import itertools
>>> t = [[1,2,3], [4,5], [6,7]]
>>> [x for x in itertools.product(*t[::-1])]
[(6, 4, 1),
 (6, 4, 2),
 (6, 4, 3),
 (6, 5, 1),
 (6, 5, 2),
 (6, 5, 3),
 (7, 4, 1),
 (7, 4, 2),
 (7, 4, 3),
 (7, 5, 1),
 (7, 5, 2),
 (7, 5, 3)]
>>> [list(x) for x in itertools.product(*t[::-1])]
[[6, 4, 1],
 [6, 4, 2],
 [6, 4, 3],
 [6, 5, 1],
 [6, 5, 2],
 [6, 5, 3],
 [7, 4, 1],
 [7, 4, 2],
 [7, 4, 3],
 [7, 5, 1],
 [7, 5, 2],
 [7, 5, 3]]

answered Oct 11, 2013 at 9:00

falsetru

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1 Comment

justhalf Over a year ago

You beat me to it! =D

Carsten · Accepted Answer · 2013-10-11 09:01:29Z

2

Use itertools.product:

In [1]: import itertools

In [2]: t = [[1,2,3], [4,5], [6,7]]

In [3]: list(itertools.product(*t[::-1]))
Out[3]:
[(6, 4, 1),
 (6, 4, 2),
 (6, 4, 3),
 (6, 5, 1),
 (6, 5, 2),
 (6, 5, 3),
 (7, 4, 1),
 (7, 4, 2),
 (7, 4, 3),
 (7, 5, 1),
 (7, 5, 2),
 (7, 5, 3)]

answered Oct 11, 2013 at 9:01

Carsten

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Comments

user27030 · Accepted Answer · 2013-10-11 09:03:00Z

0

Have a look at the itertools module. The itertools.product function does what you want, except you may want to reverse the input order.

answered Oct 11, 2013 at 9:03

user27030

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