"setting an array element with a sequence" error could be improved. #6584
Comments
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This is a duplicate of #5303. |
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indeed, sorry for the noise. |
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Re-opening in light of #5303 (comment). There are a few different but related issues. One issue is explicit vs. implicit We could keep this issue open, for improving the error message for specific cases like Here are a few more cases that give the same error message, but which may or may not be in the scope of this issue. >>> np.array([[[1, 2], [3, 4], [5, 6]], [[1], [2], [3]]], dtype=int)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: setting an array element with a sequence.>>> np.array([[1, 2, 3], 4], dtype=int)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: setting an array element with a sequence.>>> np.array([(1, 2), (2, 3, 4)], dtype=int)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: setting an array element with a sequence. |
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Thanks for your summary. I think we are on the same page. |
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Here's an analogous example with structured arrays, giving a different error message. >>> np.array([[(1, 1), (2, 2)], [(2, 2), (3, 3), (4, 4)]], dtype=[('foo', '>i4'), ('bar', '>i4')])
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: expected a readable buffer objectWhen the lists are conformable there is no error. >>> np.array([[(1, 1), (2, 2), (3, 3)], [(2, 2), (3, 3), (4, 4)]], dtype=[('foo', '>i4'), ('bar', '>i4')])
array([[(1, 1), (2, 2), (3, 3)],
[(2, 2), (3, 3), (4, 4)]],
dtype=[('foo', '>i4'), ('bar', '>i4')]) |
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I wanna bump this in sight of the BoF in terms of directions. I think better error messages in general would be great, with this my "favorite" examples. |
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Thanks @amueller. This has 31 thumbs up, clearly valuable - tagging for the next release to make sure it doesn't drift down the list again. A new issue/strategy for better error messages in general would also be useful. Could be good to discuss during the sprint. |
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I tried to think about others and/or come up with general strategies but drew a blank. Maybe looking at highly voted stack overflow issues might help to find common problems? (Gonna do that for sklearn right now lol). |
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Hmm most errors are install errors or this one lol https://stackoverflow.com/search?q=%5Bnumpy%5D+error&tab=votes |
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I removed the 1.18.0 milestone. We're not forgetting about this! There are new designs in progress that will affect this issue, but they will not be implemented for 1.18. |
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I have a branch, where the first example will give this: I could try to make it more useful, any suggestions? |
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Thanks for working on this, this is already much better! Do you keep the first part for backward compatibility? It's not really meaningful to a user, right? |
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Yeah, I thought so, plus there are some stranger paths, where we give this error but do not have the context. Although, I suppose there may not be a need to align those, because in those other paths the message is more logic, because it ends up being things like Thats true, that would be nice. I could give the first inhomogeneous part, but it may be hard to report the element where the mismatch occurred. Maybe something for later, rephrasing I can do now. I also have a "failed shape", but I would need two values for the mismatched dimension, and ideally know where exactly the mismatch was. I won't look at it right now, but I think after my PR is in, it may be possible (or at least easier) to expand the message! |
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I think this is already a big improvement, there's definitely a trade-off in how much detail to provide. |
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I am going to close the issue now, since gh-16200 is in, and the error is now better. But, I admit there is probably still a lot of room for improvement (if just rephrasing), and that is now much easier to do, so I invite contributions or suggestions! |
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I have a 3-D numpy array and im getting the same error if i try to change its dataype to float. Also, if i try using the same data without changing anything with sklearn I get the same error while if I use it with keras, I get |
This is a bit of a nitpick, but I think this would improve user-friendlyness.
Currently
np.asarray([[1, 2], [2, 3, 4]], dtype=np.float)yields "setting an array element with a sequence."I think it would be more helpful if it yielded something like "Can't create array from lists. Column length %d of column %d doesn't match column length %d."
I imagine the error bubbles up from somewhere deep in the code and makes perfect sense where it is raised. It is just something that comes up a lot, and a more friendly and / or informative message could be helpful. So maybe we could catch it further up and include more information if possible.
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