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GH571 Update typehint when creating a Series from an empty list #1029

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Merged
merged 3 commits into from
Nov 11, 2024
Merged

GH571 Update typehint when creating a Series from an empty list #1029

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01736d7
GH571 Update typehint when creating a Series from an empty list
loicdiridollou Nov 10, 2024
8f1694c
GH571 Change import source of Never to typing_extensions
loicdiridollou Nov 10, 2024
85c1e2a
GH571 PR feedback
loicdiridollou Nov 11, 2024
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10 changes: 10 additions & 0 deletions pandas-stubs/core/series.pyi
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Original file line number Diff line number Diff line change
Expand Up @@ -241,6 +241,16 @@ class Series(IndexOpsMixin[S1], NDFrame):
copy: bool = ...,
) -> Series[float]: ...
@overload
def __new__( # type: ignore[overload-overlap]
cls,
data: Sequence[Never],
index: Axes | None = ...,
*,
dtype: Dtype = ...,
name: Hashable = ...,
copy: bool = ...,
) -> Series[Any]: ...
@overload
def __new__(
cls,
data: (
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8 changes: 8 additions & 0 deletions tests/test_frame.py
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
Iterator,
Mapping,
MutableMapping,
Sequence,
)
import csv
import datetime
Expand Down Expand Up @@ -38,6 +39,7 @@
from pandas.core.series import Series
import pytest
from typing_extensions import (
Never,
TypeAlias,
assert_never,
assert_type,
Expand Down Expand Up @@ -3556,3 +3558,9 @@ class MyDict(TypedDict):
my_dict = MyDict(a="", b="")
sr = pd.Series(my_dict)
check(assert_type(sr, pd.Series), pd.Series)


def test_series_empty_dtype() -> None:
"""Test for the creation of a Series from an empty list GH571."""
new_tab: Sequence[Never] = []
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For the test, it should work without setting a type for new_tab. So if you change this line to new_tab = [], does the empty list match Sequence[Never] ?

also, double check that passing an empty string will NOT match this, because strings are sequences, and I'm not sure if "" would be an OK match for Sequence[Never]

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Thanks for the feedback, in order:

  • mypy raises an error when instantiating an empty sequence so I needed to annotate it
===========================================
Beginning: 'Run mypy on 'tests' (using the local stubs) and on the local stubs'
===========================================

tests/test_frame.py:3566: error: Need type annotation for "new_tab" (hint: "new_tab: list[<type>] = ...")  [var-annotated]
Found 1 error in 1 file (checked 226 source files)
  • I have added a test for the empty string

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FYI this is the error that you get when trying to typehint "" as a Sequence[Never] so the types are well separated.

tests/test_frame.py:3571: error: Incompatible types in assignment (expression has type "str", variable has type "Sequence[Never]")  [assignment]

for mypy above and pyright below

Diagnostics: 
Type "Literal['']" is not assignable to declared type "Sequence[Never]"  
"Literal['']" is not assignable to "Sequence[Never]"                         
Type parameter "_T_co@Sequence" is covariant, but "str" is not a subtype of "Never"
Type "str" is not assignable to type "Never" [reportAssignmentType]

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OK, I see that you added an explicit test for pd.Series([]), so the issue with new_tab is nothing to worry about.

check(assert_type(pd.Series(new_tab), "pd.Series[Any]"), pd.Series)
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