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[ENH]: Use repr instead of str in the error message #21959
Description
Problem
I mistakenly supplied "blue\n" as the argument c for matplotlib.axes.Axes.scatter , then matplitlib claimed for illegal color name like this:
ValueError: 'c' argument must be a color, a sequence of colors, or a sequence of numbers, not blue
I was not aware that the argument actually contained a trailing newline so I was very confused.
Proposed solution
The error message would be nicer if it outputs user's input via repr.
For example, in this case the error message here can be easily replced with:
raise ValueError(
f"'c' argument must be a color, a sequence of colors, "
f"or a sequence of numbers, not {c!r}") from so that we may now get an easy-to-troubleshoot error like this:
ValueError: 'c' argument must be a color, a sequence of colors, or a sequence of numbers, not "blue\n"
This kind of improvement can be applied to many other places.
Activity
tacaswell commented on Dec 15, 2021
Labeling this as a good first issue as this is a straight forward change that should not bring up any API design issues (yes technically changing the wording of an error message may break someone, but that is so brittle I am not going to worry about that). Will need a test (the new line example is a good one!).
tacaswell commented on Dec 15, 2021
@e5f6bd If you are interested in opening a PR with this change, please have at it!
e5f6bd commented on Dec 15, 2021
@e5f6bd Thanks, but I'm a bit busy recently, so I'll leave this chance to someone else.
Hashcode-Ankit commented on Dec 29, 2021
If this issue has not been resolved yet and nobody working on it I would like to try it
story645 commented on Dec 29, 2021
Looks like #21968 is addressing this issue
Hashcode-Ankit commented on Dec 29, 2021
yeah but the issue still open
Cloverwave commented on Jul 1, 2022
Working on this now in axes_.py,
future plans to work on this in all files with error raising.
Cloverwave commented on Jul 1, 2022
Also converting f strings to template strings where I see them in raised errors
oscargus commented on Jul 4, 2022
f-string are usually preferred due to speed issues. Which is not critical, but if one can choose, f-strings are not worse.
use `repr` in error message closes matplotlib#21959
use `repr` in error message closes matplotlib#21959
use repr in error message closes matplotlib#21959
Use `repr` in scatter error message (#24403)
Use `repr` in scatter error message (matplotlib#24403)