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TYP: Add TypeVars to NDFrame #30613

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Jan 3, 2020
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9 changes: 9 additions & 0 deletions pandas/core/base.py
Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
import numpy as np

import pandas._libs.lib as lib
from pandas._typing import T
from pandas.compat import PYPY
from pandas.compat.numpy import function as nv
from pandas.errors import AbstractMethodError
Expand Down Expand Up @@ -87,6 +88,14 @@ def __sizeof__(self):
# object's 'sizeof'
return super().__sizeof__()

def _ensure_type(self: T, obj) -> T:
"""Ensure that an object has same type as self.

Used by type checkers.
"""
assert isinstance(obj, type(self)), type(obj)

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This line breaks any code that creates a subclass of the pandas.core.frame.DataFrame. issubclass should be used instead.

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Yes, see also #31925 (maybe repeat your comment there). We should fix this for 1.0.2

return obj


class NoNewAttributesMixin:
"""Mixin which prevents adding new attributes.
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