Merge two numpy arrays into a list of lists of tuples

Question

I haven't been able to figure this out. Thanks for any help:

Have:

>>> x = np.array([[1,2],[5,6]])
>>> x
array([[1, 2],
       [5, 6]])
>>> y = np.array([[3,4],[7,8]])
>>> y
array([[3, 4],
       [7, 8]])

Want:

>>> z = [[(1,2),(3,4)],[(5,6),(7,8)]]
>>> z
[[(1, 2), (3, 4)], [(5, 6), (7, 8)]]

Possible duplicate of [Convert numpy array to tuple](https://stackoverflow.com/questions/10016352/convert-numpy-array-to-tuple) — gdlmx, Mar 01 '19 at 01:16

score 3 · Accepted Answer · answered Feb 28 '19 at 21:25

3

Try this:

x_z = map(tuple,x)
y_z = map(tuple,y)
[list(i) for i in zip(x_z, y_z)]

Output:

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

answered Feb 28 '19 at 21:25

Scott Boston

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Thanks, this looks like the most straightforward solution. – llevar Mar 01 '19 at 08:07

score 2 · Answer 2 · answered Mar 01 '19 at 02:18

This is a fun problem. Here's what I came up with:

print([list(map(tuple, i)) for i in zip(x, y)])
# [[(1, 2), (3, 4)], [(5, 6), (7, 8)]]

Basically, zipping x and y gets you:

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

and so then you convert each element first into a list, and then a tuple

Draconis · Answer 3 · 2019-02-28T21:41:55.153

0

If you want to run through the rows of each matrix, you can do this:

for (row1, row2) in zip(x,y):
    yield [tuple(row1), tuple(row2)]
       #  [ (1,2)     ,  (3,4)     ]

This will give you a generator (if you wrap it in a function), but you want a list. So instead, wrap it in a comprehension:

[ [tuple(row1),tuple(row2)] for (row1, row2) in zip(x,y) ]

edited Feb 28 '19 at 21:41

answered Feb 28 '19 at 21:20

Draconis

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you should specify that the `yield` version needs to be inside a function definition – gold_cy Feb 28 '19 at 21:31

score 0 · Answer 4 · answered Feb 28 '19 at 21:25

0

x = list([[1,2],[5,6]])
y = list([[3,4],[7,8]])
x
[[1, 2], [5, 6]]
y
[[3, 4], [7, 8]]
z=list(zip(x,y))
z
[([1, 2], [3, 4]), ([5, 6], [7, 8])]

answered Feb 28 '19 at 21:25

Ray

59
5

Thanks, but this produces a list of tuples of lists, not a list of lists of tuples as requested. – llevar Mar 01 '19 at 07:56

score 0 · Answer 5 · answered Mar 01 '19 at 00:06

0

IIUC

z=np.array([x,y])
[list(map(tuple,z[:,x]))for x in range(len(x))]
Out[223]: [[(1, 2), (3, 4)], [(5, 6), (7, 8)]]

answered Mar 01 '19 at 00:06

BENY

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fountainhead · Answer 6 · 2019-03-01T04:14:50.703

For what it's worth, here's the simplest and most efficient (but probably the least generalized) solution:

result = [[(x[0,0], x[0,1]), (y[0,0], y[0,1])],
         [(x[1,0], x[1,1]), (y[1,0], y[1,1])]]

Output:

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

Admittedly, it doesn't generalize, but the question is -- in which direction is generalization required? Longer outer dimension? Longer inner dimension? The question hasn't called for any generalization.

Based on explicitly stated requirement, this solution can of course be modified to make it generalized just as much as needed.

Merge two numpy arrays into a list of lists of tuples

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