BUG: to_numpy_dtype_inference returns None when array is non-numeric and dtype isn't given · Issue #56991 · pandas-dev/pandas (original) (raw)

Pandas version checks

Reproducible Example

mport numpy as np from pandas.core.arrays._utils import to_numpy_dtype_inference

Issue 1: ArrayLike type of np.ndarray doesn't have atrribute .dtype.numpy_dtype

try: to_numpy_dtype_inference(np.array([1,2,3]), None, np.nan, False) except Exception as e: print(e)

Issue 2: If dtype isn't given and array is not a numeric dtype, returned dtype is None

print(to_numpy_dtype_inference(np.array(['b','b','c']), None, np.nan, False))

Issue Description

Two places in utility method 'to_numpy_dtype_inference' have issues. The first is that the input array arg "arr" can be of type[ndarray] but ndarray doesn't have an attribute ".dtype.numpy_dtype". The second is that non-numeric array inputs without a given dtype will return None instead of np.dtype(np.object_)

def to_numpy_dtype_inference( arr: ArrayLike, dtype: npt.DTypeLike | None, na_value, hasna: bool ) -> tuple[npt.DTypeLike, Any]: if dtype is None and is_numeric_dtype(arr.dtype): dtype_given = False if hasna: if arr.dtype.kind == "b": dtype = np.dtype(np.object_) else: if arr.dtype.kind in "iu": dtype = np.dtype(np.float64) else: dtype = arr.dtype.numpy_dtype # type: ignore[union-attr] # <-- Issue 1 if na_value is lib.no_default: na_value = np.nan else: dtype = arr.dtype.numpy_dtype # type: ignore[union-attr] elif dtype is not None: dtype = np.dtype(dtype) dtype_given = True else: dtype_given = True # <-- Issue 2 [this should instead be "dtype = np.dtype(np.object_)"]

if na_value is lib.no_default:
    na_value = arr.dtype.na_value

if not dtype_given and hasna:
    try:
        np_can_hold_element(dtype, na_value)  # type: ignore[arg-type]
    except LossySetitemError:
        dtype = np.dtype(np.object_)
return dtype, na_value

Expected Behavior

Issue 1: This case doesn't apply to me so I don't have any expectation other than Pandas shouldn't throw an exception.
Issue 2: return np.dtype(np.object_) when array is non-numeric and dtype is not provided

Installed Versions

INSTALLED VERSIONS

commit : f538741
python : 3.10.13.final.0
python-bits : 64
OS : Darwin
OS-release : 23.2.0
Version : Darwin Kernel Version 23.2.0: Wed Nov 15 21:53:34 PST 2023; root:xnu-10002.61.3~2/RELEASE_ARM64_T8103
machine : arm64
processor : arm
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 2.2.0
numpy : 1.26.3
pytz : 2023.3.post1
dateutil : 2.8.2
setuptools : 69.0.3
pip : 23.3.2
Cython : None
pytest : 7.4.4
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.1.3
IPython : None
pandas_datareader : None
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : None
bottleneck : None
dataframe-api-compat : None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : 3.8.2
numba : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : 14.0.2
pyreadstat : None
python-calamine : None
pyxlsb : None
s3fs : None
scipy : 1.11.4
sqlalchemy : None
tables : None
tabulate : None
xarray : 2024.1.0
xlrd : None
zstandard : 0.22.0
tzdata : 2023.4
qtpy : None
pyqt5 : None