BUG: inconsistent behaviour for empty DataFrames #48327
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ntachukwu
commented
Aug 31, 2022
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ntachukwu
commented
- Closes API: Specify the behaviour for operating on empty objects #47959
- Tests added
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Hello @Th3nn3ss! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found: There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻 Comment last updated at 2022-09-08 07:55:53 UTC |
pandas/tests/groupby/test_apply.py
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| import datetime as dt | |||
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The datetime module is already imported below as well (so you can update your code to use the existing import)
pandas/tests/groupby/test_apply.py
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| df3 = df2.set_index("date").groupby("a", group_keys=True).apply(lambda x: x) | ||
| expected = df3.iloc[:0] # An empty dataframe | ||
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| tm.assert_equal(result, expected) |
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| tm.assert_equal(result, expected) | |
| tm.assert_frame_equal(result, expected) |
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@jorisvandenbossche Yes, The idea is to show some inconsistencies with empty inputs with some failing tests. I will love to fix it. |
| result_empty = pd.DataFrame([]) | ||
| expected_empty = pd.DataFrame(pd.Series([])) | ||
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| tm.assert_frame_equal(result_empty, expected_empty) |
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Error returned
E AssertionError: DataFrame are different
E
E DataFrame shape mismatch
E [left]: (0, 0)
E [right]: (0, 1)
pandas/tests/frame/test_constructors.py:3211: AssertionError
| result = pd.DataFrame({"a": [], "b": []}) | ||
| expected = pd.DataFrame(columns=["a", "b"]) | ||
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| tm.assert_frame_equal(result, expected) |
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Error
E AssertionError: DataFrame.index are different
E
E DataFrame.index classes are different
E [left]: RangeIndex(start=0, stop=0, step=1)
E [right]: Index([], dtype='object')
pandas/_testing/asserters.py:318: AssertionError
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| with tm.assert_produces_warning(FutureWarning): | ||
| # Lists does not warn the user | ||
| result = pd.DataFrame({"a": [], "b": []}) |
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Error
E AssertionError: Did not see expected warning of class 'FutureWarning'
pandas/_testing/_warnings.py:143: AssertionError
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>>> df_with_series = pd.DataFrame({"a": pd.Series([]), "b": pd.Series([])}) # Prints a warning
<stdin>:1: FutureWarning: The default dtype for empty Series will be 'object' instead of 'float64' in a future version. Specify a dtype explicitly to silence this warning.
>>> df_with_list = pd.DataFrame({"a": [], "b": []}) # Does not print a warning
>>> tm.assert_frame_equal(df_with_series, df_with_list) # Both df are equal
| df3 = df2.set_index("date").groupby("a", group_keys=True).apply(lambda x: x) | ||
| expected = df3.iloc[:0] # An empty dataframe | ||
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| tm.assert_frame_equal(result, expected) |
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Error
E AssertionError: DataFrame.index are different
E
E DataFrame.index classes are different
E [left]: Int64Index([], dtype='int64', name='a')
E [right]: MultiIndex([], names=['a', 'date'])
pandas/_testing/asserters.py:318: AssertionError
mroeschke
added
Testing
| def test_groupby_sample_with_empty_inputs(): | ||
| df = DataFrame({"a": [], "b": []}) | ||
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| gb_df = df.groupby("a").sample() |
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---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
Input In [1], in <cell line: 3>()
1 empty_df = pd.DataFrame({'a': [], 'b': []})
----> 2 empty_df.groupby('a').sample()
File ~.../pandas/core/groupby/groupby.py:4284, in sample(self, n, frac, replace, weights, random_state)
4275 assert frac is not None
4276 sample_size = round(frac * group_size)
4278 grp_sample = sample.sample(
4279 group_size,
4280 size=sample_size,
4281 replace=replace,
4282 weights=None if weights is None else weights_arr[grp_indices],
4283 random_state=random_state,
-> 4284 )
4285 sampled_indices.append(grp_indices[grp_sample])
4287 sampled_indices = np.concatenate(sampled_indices)
File <__array_function__ internals>:180, in concatenate(*args, **kwargs)
ValueError: need at least one array to concatenate
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This pull request is stale because it has been open for thirty days with no activity. Please update and respond to this comment if you're still interested in working on this. |
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Still working on this @Th3nn3ss or has this been superseded with your other work? |
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Thanks for the pull request, but it appears to have gone stale. If interested in continuing, please merge in the main branch, address any review comments and/or failing tests, and we can reopen. |
