Is there a function to transpose matrices (lists of lists) in python? if rows not equal column

Question

Is there a function to convert matrices in python? example [1,2],[4,5],[7,8] => ans : [1,4,7],[2,5,8]

I would call this operation "transpose" rather than "convert" (which could mean anything). — Blckknght, Jan 25 '14 at 07:59

score 3 · Accepted Answer · answered Jan 25 '14 at 07:57

3

You can use zip function, like this

l = [[1,2,3],[4,5,6],[7,8,9]]
print zip(*l)

Output

[(1, 4, 7), (2, 5, 8), (3, 6, 9)]

answered Jan 25 '14 at 07:57

thefourtheye

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what a clever use of zip and argument expansion – Yanshuai Cao Jan 25 '14 at 08:07
@caoy People used to call this as argument unpacking :) – thefourtheye Jan 25 '14 at 08:08
lol, thanks, i knew i shouldn't just invent names :P – Yanshuai Cao Jan 25 '14 at 08:36
@ thefourtheye if rows not equal columns. example [[1,2,3,4],[5,6,7,8],[9,0,11,12]] output [[1,5,9],[2,6,0],[3,7,11],[4,8,12]] – pukluk Jan 25 '14 at 08:53
@pukluk It will still work. Please try that yourself :) – thefourtheye Jan 25 '14 at 08:54

score 2 · Answer 2 · answered Jan 25 '14 at 08:05

2

Depending on your program, you may want to use numpy:

In [1]: m = np.array([[1,2,3],[4,5,6],[7,8,9]])

In [2]: m
Out[2]: 
array([[1, 2, 3],
       [4, 5, 6],
       [7, 8, 9]])

In [3]: m.T
Out[3]: 
array([[1, 4, 7],
       [2, 5, 8],
       [3, 6, 9]])

answered Jan 25 '14 at 08:05

alecbz

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if rows not equal columns. example [[1,2,3,4],[5,6,7,8],[9,0,11,12]] output [[1,5,9],[2,6,0],[3,7,11],[4,8,12]] – pukluk Jan 25 '14 at 08:52
This will still work in numpy. – alecbz Jan 25 '14 at 19:21

Is there a function to transpose matrices (lists of lists) in python? if rows not equal column

2 Answers2