Convert any multi-dimensional numpy array to tuple of tuples of tuples... agnostic of number of dimensions

Question

That this answer to Convert numpy ndarray to tuple of tuples in optimize method doens't offer anything more than tuple(tuple(i) for i in a[:,0,:]) suggests this doesn't exist, but I am looking for something like a .totuple() method similar to numpy's .tolist() in that you don't need to know the number of dimensions beforehand to generate a tuple of tuples of tuples...

For my needs this would apply to a float or integer numerical array only.

``numpy` does not have hidden methods! For most purposes tolists is sufficient, and faster than any iteration on an array. It also takes the conversion all the way down, producing python end values (i.e. int instead of np.int64). — hpaulj
– hpaulj, Commented Jul 13, 2021 at 12:52
@hpaulj thanks, I have a hunch that JelleWestra's answer is as good as it's going to get. I'll see if I can make .tolist() work for me. If there's no totupple() there must be some reason for that. Is there a PEP for I Do Not Want What I Haven't Got? :-) — uhoh
– uhoh, Commented Jul 13, 2021 at 13:03
@user76284 after seeing your nice answer I thought about it, but 1) an n-nested tuple is a weird thing, it would then want a shape method of its own (I had to print b[0][0][0][0] to see if b = totuple(np.arange(2**5).reshape(*5*[2])) worked). Usually feature requests need to make a good case for a real need; "What problems/challenges does it solve?" I wouldn't know how to argue such a thing. — uhoh
– uhoh, Commented Mar 13, 2023 at 7:20
@uhoh One common use case is getting a hashable and immutable representation of an array, e.g. to store in a set or as a key in a dictionary. (In this respect, it's more useful than tolist.) There are many questions on SO about converting an array to a nested tuple. These could perhaps be used as examples. — user76284
– user76284, Commented Mar 13, 2023 at 15:38

user76284 · Accepted Answer · 2023-03-13 06:46:19Z

2

A more explicit alternative:

def totuple(a):
    if a.shape == ():
        return a.item()
    else:
        return tuple(map(totuple, a))

Example:

import numpy as np
a = np.arange(3 * 4).reshape(3, 4)
print(totuple(a))

((0, 1, 2, 3), (4, 5, 6, 7), (8, 9, 10, 11))

answered Mar 13, 2023 at 6:46

user76284

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1 Comment

uhoh Over a year ago

Nice! Zen of Python 'Explicit is better than implicit'

Jelle Westra · Accepted Answer · 2021-07-13 12:05:35Z

2

You can make use of a recursive function which converts to a tuple independent of the number of dimensions:

def totuple(a):
    try:
        return tuple(totuple(i) for i in a)
    except TypeError:
        return a

Found in this answer: Convert numpy array to tuple

answered Jul 13, 2021 at 12:05

Jelle Westra

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3 Comments

uhoh Over a year ago

Interesting! I will give it a try. I was hoping for "something like a .totuple() method similar to numpy's .tolist()" so I wouldn't have to rewrite it every time I need it, but it may not exist.

Jelle Westra Over a year ago

@uhoh As far as I'm aware, there doesn't exist such a method or function in numpy unfortunately.

hpaulj Over a year ago

Applying this function to the tolist result is probably faster.

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