Added Documentation to specify that DataFrame.last() needs the index to be sorted to deliver the expected results #38536
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Added Documentation mentioning that DataFrame.last() needs the index to be sorted to deliver the expected results
Fixed PEP8 Issues
Fixed PEP 8 Issues
pandas/core/generic.py
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| @@ -8442,6 +8442,9 @@ def last(self: FrameOrSeries, offset) -> FrameOrSeries: | |||
| When having a DataFrame with dates as index, this function can | |||
| select the last few rows based on a date offset. | |||
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| Note that for the last() method to work, the DatetimeIndex | |||
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Personal opinion but I'd rather rephrase the paragraph above to make this clear:
For a DataFrame with a sorted DatetimeIndex, this function selects the last few rows based on a date offset.
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Yeah this seems to be better, I wasn't thinking of changing the original section initially but if that's okay then I'll change that too thanks :)
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@arw2019 I did make the changes but I was wondering as was commented in the issue earlier as well do we need to raise an error message as well incase the index is not sorted?
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@arw2019 I did make the changes but I was wondering as was commented in the issue earlier as well do we need to raise an error message as well incase the index is not sorted?
It uses binary search under the hood (logarithmic time) so, given no extra information, vertifying sortedness (linear time) would degrade performance. If sortedness information is stored somehow then I agree we should throw but AFAIK it isn't in general for a DatetimeIndex.
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ohkk understood thanks 👍
As per recommendation changed the description for DataFrame.last() making it more concise
Removed trailing whitespace to fix PEP 8 Issues
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Thanks @MarcoGorelli |
…to be sorted to deliver the expected results (pandas-dev#38536) * Update generic.py Added Documentation mentioning that DataFrame.last() needs the index to be sorted to deliver the expected results * Update generic.py Fixed PEP8 Issues * Update generic.py Fixed PEP 8 Issues * Update generic.py As per recommendation changed the description for DataFrame.last() making it more concise * Update generic.py Removed trailing whitespace to fix PEP 8 Issues
Added Documentation mentioning that DataFrame.last() needs the index to be sorted to deliver the expected results
Haven't yet worked on raising an error will work as advised
black pandasgit diff upstream/master -u -- "*.py" | flake8 --diff