8000 PERF: construct DataFrame with string array and dtype=str by topper-123 · Pull Request #36432 · pandas-dev/pandas · GitHub
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PERF: construct DataFrame with string array and dtype=str #36432

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Merged
merged 4 commits into from
Sep 19, 2020
Merged

PERF: construct DataFrame with string array and dtype=str #36432

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439d17a
PERF: construct DataFrame with string array and dtype=str
topper-123 Sep 17, 2020
f1d66cb
add GH number
topper-123 Sep 17, 2020
5d1dd81
fix dtype issues
topper-123 Sep 17, 2020
256ad70
add ASVs
topper-123 Sep 19, 2020
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PERF: construct DataFrame with string array and dtype=str
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@topper-123
topper-123 committed Sep 19, 2020
commit 439d17ae739f3c465867f8276067b428af730473
2 changes: 1 addition & 1 deletion pandas/core/dtypes/cast.py
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Expand Up @@ -1618,7 +1618,7 @@ def construct_1d_ndarray_preserving_na(
array(['1.0', '2.0', None], dtype=object)
"""

if dtype is not None and dtype.kind == "U":
if is_string_dtype(dtype):
subarr = lib.ensure_string_array(values, convert_na_value=False, copy=copy)
else:
subarr = np.array(values, dtype=dtype, copy=copy)
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20 changes: 11 additions & 9 deletions pandas/core/internals/construction.py
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Expand Up @@ -13,6 +13,7 @@

from pandas.core.dtypes.cast import (
construct_1d_arraylike_from_scalar,
construct_1d_ndarray_preserving_na,
maybe_cast_to_datetime,
maybe_convert_platform,
maybe_infer_to_datetimelike,
Expand Down Expand Up @@ -189,15 +190,16 @@ def init_ndarray(values, index, columns, dtype: Optional[DtypeObj], copy: bool):
# the dtypes will be coerced to a single dtype
values = _prep_ndarray(values, copy=copy)

if dtype is not None:
if not is_dtype_equal(values.dtype, dtype):
try:
values = values.astype(dtype)
except Exception as orig:
# e.g. ValueError when trying to cast object dtype to float64
raise ValueError(
f"failed to cast to '{dtype}' (Exception was: {orig})"
) from orig
if not is_dtype_equal(values.dtype, dtype):
try:
values = construct_1d_ndarray_preserving_na(
values.ravel(), dtype=dtype, copy=False
).reshape(values.shape)
except Exception as orig:
# e.g. ValueError when trying to cast object dtype to float64
raise ValueError(
f"failed to cast to '{dtype}' (Exception was: {orig})"
) from orig
45EF
# _prep_ndarray ensures that values.ndim == 2 at this point
index, columns = _get_axes(
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