DOC: explain the mode.chained_assignment option
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doc/source/indexing.rst
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| You can control the action of a chained assignment via the option ``mode.chained_assignment``, | ||
| which can take the values ``['raise','warn',None]``, where showing a warning is the default. | ||
| When using chained indexing, the order may determine whether a copy is returned |
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I agree that merely 'the order' is not explicit enough. Now that I am looking closer, though, I would say it's not the order of evaluation, but the order in which the user chains the indexing operations (which in turn determines the order the operations are evaluated).
I have turned the sentence into this, which I hope is also in the spirit of your edit:
When you use chained indexing, the order and type of the indexing operation
partially determine whether the result is a slice into the original object, or
a copy of the slice.
What do you think of that? I don't mean to make this a bikeshedding point, so I will implement whatever you suggest as the final version.
doc/source/indexing.rst
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| Pandas has the ``SettingWithCopyWarning`` because assigning to a copy of a | ||
| slice is frequently not intentional, but a mistake caused by chained indexing | ||
| returning a copy where a slice was expected. If you would like pandas to be |
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paragraph break after first sentence
doc/source/indexing.rst
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| slice is frequently not intentional, but a mistake caused by chained indexing | ||
| returning a copy where a slice was expected. If you would like pandas to be | ||
| more or less trusting about assignment to a chained indexing expression, you | ||
| can set the :ref:`option <options>` ``mode.chained_assignment``, which can take |
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use a bulleted list for these options
Codecov Report
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Codecov Report
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## master #18635 +/- ##
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- Coverage 91.59% 91.54% -0.05%
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doc/source/indexing.rst
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| which can take the values ``['raise','warn',None]``, where showing a warning is the default. | ||
| * ``'raise'`` means pandas will raise a ``SettingWithCopyException`` exception | ||
| you have to deal with. | ||
| * ``'warn'``, the default, means a ``SettingWithCopyWarning`` is printed. |
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@jreback I've put the default first, and the checks have passed. Does 'ping on green' mean to send you a message when this is done? If yes, this is your ping. I forgot to say this last time I replied, so I'll say it now: thank you very much! Not just for the review, but for all the work you do for the pandas project. It is very much appreciated. |
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@sietse Thanks a lot! (I fixed the conflict, due to another PR that was just merged) |
git diff upstream/master -u -- "*.py" | flake8 --diffMake the explanation of the
mode.chained_assignmentoption link to the explanation of chained indexing and assignment. Explain what the three possible settings do.