head(0) and tail(0) return empty DataFrames #11937
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| return self | ||
| if n == 0: | ||
| return self.iloc[l:] |
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I think self.iloc[0:0] is clearer here. I don't think you need l anymore (was it ever needed?).
The side question here is: should we check that n>0? I don't think we need to... as this will make it kinda useful: it'll return the rest of the dataframe except the head(n) == tail(len(df) - n).
Edit: or n>=0.
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make sure to test groupby! (need updating maybe) |
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Fixing the broken unit test.... |
| @@ -2146,8 +2147,10 @@ def tail(self, n=5): | |||
| Returns last n rows | |||
| """ | |||
| l = len(self) | |||
| if l == 0 or n == 0: | |||
| if l == 0: | |||
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This l is not required. self.iloc[-0:] == self :)
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So why was it there in the first place? I don't really understand what its doing in either head() or tail().
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I think it was due to the n == 0 or n == l check that was there before. Even in that case there's no need to avoid the iloc in the latter case; code is simpler without it.
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groupby is already tested: https://github.com/pydata/pandas/blob/a89f48940cd0a7346302311011beb3a09e9be292/pandas/tests/test_groupby.py#L1912-L1913. thanks! lgtm, but please squash. |
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I don't really understand why Travis is failing - it seems to be some kind of connection error? Is that something I've done wrong? |
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Looks unrelated. squash and maybe the tests will pass next time :) |
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I'm sorry, I'm not sure what you mean by 'squash'. |
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Ah, ok. I think I did that right, hopefully the tests will pass this time. |
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Need more thing, a release note in |
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Added a note in the release docs. |
| @@ -166,6 +166,7 @@ Backwards incompatible API changes | |||
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| - The parameter ``out`` has been removed from the ``Series.round()`` method. (:issue:`11763`) | |||
| - ``DataFrame.round()`` leaves non-numeric columns unchanged in its return, rather than raises. (:issue:`11885`) | |||
| - ``DataFrame.head(0)`` and ``DataFrame.tail(0)`` return empty frames, rather than ``self``. (:issue:`11937`) | |||
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Mention Series as well here
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actually Series was already doing this. But that's fine.
unit test for Series.head(0), Series.tail(0) fixed breaking unit tests on Series.head(0)/Series.tail(0) removed unnecessary length checks added documentation mention series in API docs
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ok, lgtm. ping when green. |
head(0) and tail(0) return empty DataFrames
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Great! |
closes #11930
frame.head(0) and frame.tail(0) now return empty DataFrames.