Code review for adding axis argument to permutation and shuffle function
Hi,
I would like to request a code review. The random.permutation and random.shuffle functions now can only shuffle along the first axis of a multidimensional array. I propose to add an axis argument for the functions and allow them to shuffle along a given axis. Here is the link to the PR (https://github.com/numpy/numpy/pull/13829).
Thanks!
This proposal to add an axis argument to permutation and shuffle seems to have garnered no reply. Are people OK with it (for the new random.Generator only) ?
 Sent from: http://numpydiscussion.10968.n7.nabble.com/
I don’t understand why the proposal would be controversial in any way. It’s very natural to have `axis=` keyword arguments in NumPy, and it’s the lack of them that is surprising. My only additional suggestion would be to allow tuples of axes, but that can come later.
Juan.
On 13 Sep 2019, at 4:25 pm, mattip matti.picus@gmail.com wrote:
This proposal to add an axis argument to permutation and shuffle seems to have garnered no reply. Are people OK with it (for the new random.Generator only) ?
 Sent from: http://numpydiscussion.10968.n7.nabble.com/ _______________________________________________ NumPyDiscussion mailing list NumPyDiscussion@python.org https://mail.python.org/mailman/listinfo/numpydiscussion
Hi,
Thanks  yes  I agree, an axis argument seems like a very sensible idea.
Cheers,
Matthew
On Fri, Sep 13, 2019 at 7:48 AM Juan NunezIglesias jni@fastmail.com wrote:
I don’t understand why the proposal would be controversial in any way. It’s very natural to have `axis=` keyword arguments in NumPy, and it’s the lack of them that is surprising. My only additional suggestion would be to allow tuples of axes, but that can come later.
Juan.
On 13 Sep 2019, at 4:25 pm, mattip matti.picus@gmail.com wrote:
This proposal to add an axis argument to permutation and shuffle seems to have garnered no reply. Are people OK with it (for the new random.Generator only) ?
 Sent from: http://numpydiscussion.10968.n7.nabble.com/ _______________________________________________ NumPyDiscussion mailing list NumPyDiscussion@python.org https://mail.python.org/mailman/listinfo/numpydiscussion
NumPyDiscussion mailing list NumPyDiscussion@python.org https://mail.python.org/mailman/listinfo/numpydiscussion
On 7/4/19, Kexuan Sun me@kianasun.com wrote:
Hi,
I would like to request a code review. The random.permutation and random.shuffle functions now can only shuffle along the first axis of a multidimensional array. I propose to add an axis argument for the functions and allow them to shuffle along a given axis. Here is the link to the PR (https://github.com/numpy/numpy/pull/13829).
Given the current semantics of 'shuffle', the proposed change makes sense. However, I would like to call attention to
https://github.com/numpy/numpy/issues/5173
and to the mailing list thread from 2014 that I started here:
https://mail.python.org/pipermail/numpydiscussion/2014October/071340.html
The topic of those discussions was that the current behavior of 'shuffle' is often *not* what users want or expect. What is often desired is to shuffle each row (or column, or whatever dimension is specified) *independently* of the others. So if
a = np.array([[0, 1, 2, 3, 4], [5, 6, 7, 8, 9], [10, 11, 12, 13, 14]]),
then randomly shuffling 'a' along axis=1 should shuffle each row independently of the others, to create something like
a = np.array([[2, 4, 0, 3, 1], [8, 6, 9, 7, 5], [11, 12, 10, 14, 13]])
An API for this was discussed (and of course that ran into the second of the two hard problems in computer science, naming things).
Take a look at those discussions, and check that
https://github.com/numpy/numpy/pull/13829
fits in with the possible changes mentioned in those discussions. If we don't use the name 'shuffle' for the new random permutation function(s), then the change in PR 13829 is a good one. However, if we want to try to reuse the name 'shuffle' to also allow independent shuffling along an axis, then we have to be careful with how we interpret the 'axis' argument.
Warren
Thanks!
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participants (5)

Juan NunezIglesias

Kexuan Sun

Matthew Brett

mattip

Warren Weckesser