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REF: simplify maybe_upcast #38428

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Merged
merged 2 commits into from
Dec 12, 2020
Merged

REF: simplify maybe_upcast #38428

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d8ced73
REF: simplify maybe_upcast
jbrockmendel Dec 12, 2020
7c0034f
CLN: remove duplicated check
jbrockmendel Dec 12, 2020
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30 changes: 8 additions & 22 deletions pandas/core/dtypes/cast.py
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Original file line number Diff line number Diff line change
Expand Up @@ -924,45 +924,31 @@ def maybe_infer_dtype_type(element):


def maybe_upcast(
values: ArrayLike,
values: np.ndarray,
fill_value: Scalar = np.nan,
dtype: Dtype = None,
copy: bool = False,
) -> Tuple[ArrayLike, Scalar]:
) -> Tuple[np.ndarray, Scalar]:
"""
Provide explicit type promotion and coercion.

Parameters
----------
values : ndarray or ExtensionArray
The array that we want to maybe upcast.
values : np.ndarray
The array that we may want to upcast.
fill_value : what we want to fill with
dtype : if None, then use the dtype of the values, else coerce to this type
copy : bool, default True
If True always make a copy even if no upcast is required.

Returns
-------
values: ndarray or ExtensionArray
values: np.ndarray
the original array, possibly upcast
fill_value:
the fill value, possibly upcast
"""
if not is_scalar(fill_value) and not is_object_dtype(values.dtype):
# We allow arbitrary fill values for object dtype
raise ValueError("fill_value must be a scalar")

if is_extension_array_dtype(values):
if copy:
values = values.copy()
else:
if dtype is None:
dtype = values.dtype
new_dtype, fill_value = maybe_promote(dtype, fill_value)
if new_dtype != values.dtype:
values = values.astype(new_dtype)
elif copy:
values = values.copy()
new_dtype, fill_value = maybe_promote(values.dtype, fill_value)
# We get a copy in all cases _except_ (values.dtype == new_dtype and not copy)
values = values.astype(new_dtype, copy=copy)

return values, fill_value

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