astype not converting timedelta and datetime strings

[fjdiod]

Code Sample, a copy-pastable example if possible

>>> s = pd.Series(['0:0:1'])
>>> s.astype('timedelta64[ns]')
WTF timedelta64[ns]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/sergey/projects/pandas/pandas/util/_decorators.py", line 177, in wrapper
    return func(*args, **kwargs)
  File "/home/sergey/projects/pandas/pandas/core/generic.py", line 5182, in astype
    **kwargs)
  File "/home/sergey/projects/pandas/pandas/core/internals/managers.py", line 554, in astype
    return self.apply('astype', dtype=dtype, **kwargs)
  File "/home/sergey/projects/pandas/pandas/core/internals/managers.py", line 421, in apply
    applied = getattr(b, f)(**kwargs)
  File "/home/sergey/projects/pandas/pandas/core/internals/blocks.py", line 564, in astype
    **kwargs)
  File "/home/sergey/projects/pandas/pandas/core/internals/blocks.py", line 655, in _astype
    values = astype_nansafe(values.ravel(), dtype, copy=True)
  File "/home/sergey/projects/pandas/pandas/core/dtypes/cast.py", line 717, in astype_nansafe
    return lib.astype_intsafe(arr.ravel(), dtype).reshape(arr.shape)
  File "pandas/_libs/lib.pyx", line 455, in pandas._libs.lib.astype_intsafe
    util.set_value_at_unsafe(result, i, v)
  File "pandas/_libs/tslibs/util.pxd", line 145, in pandas._libs.tslibs.util.set_value_at_unsafe
    assign_value_1d(arr, i, value)
ValueError: Could not convert object to NumPy timedelta

Same with datetime.

Expected Output

>>> s.astype('timedelta64[ns]')
0   00:00:01
dtype: timedelta64[ns]

Output of pd.show_versions()

INSTALLED VERSIONS

commit: 114f415
python: 3.6.6.final.0
python-bits: 64
OS: Linux
OS-release: 4.13.0-46-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8

pandas: 0.24.0.dev0+365.g114f41534.dirty
pytest: 3.6.2
pip: 10.0.1
setuptools: 39.2.0
Cython: 0.28.3
numpy: 1.14.5
scipy: 1.1.0
pyarrow: 0.9.0
xarray: 0.10.7
IPython: 6.4.0
sphinx: 1.7.5
patsy: 0.5.0
dateutil: 2.7.3
pytz: 2018.4
blosc: None
bottleneck: 1.2.1
tables: 3.4.4
numexpr: 2.6.5
feather: 0.4.0
matplotlib: 2.2.2
openpyxl: 2.5.4
xlrd: 1.1.0
xlwt: 1.3.0
xlsxwriter: 1.0.5
lxml: 4.2.2
bs4: 4.6.0
html5lib: 1.0.1
sqlalchemy: 1.2.8
pymysql: 0.8.1
psycopg2: None
jinja2: 2.10
s3fs: 0.1.5
fastparquet: 0.1.5
pandas_gbq: None
pandas_datareader: None
gcsfs: 0.1.0

[azelk]

The bug is still there. Please fix.

[jreback]

The bug is still there. Please fix.

hence the open status of this issue

@azelk you are welcome to volunteer a patch

[nathanckuhn]

I believe this is related, so I thought I'd share. (If distinct enough, please tell me & I can open a new issue.)

Summary: Below is a reproducible example similar to a project where I am trying to change large batches of Pandas DataFrame columns from 'string' to 'datetime64[ns]'. In doing so, I have gotten ValueErrors when astype() cannot convert the string date columns into date dtypes.

The issue seems arise when
(a) the string column is dtype 'string' not 'object' and
(b) the 'string' dtype column contains a mixture of string date formats.

The example below shows that to_datetime() is perfectly capable of handling both objects & 'string' dtypes, both with and without NA, and both with and without different date formats.

However, astype() cannot handle the (a)+(b) situation.
Why not? This seems like a bug.

Thanks for any thoughts!

Note: I'm running this in Visual Studio Code, hence the "#%%" interactive sections:

#%%
import pandas as pd
import numpy as np
import sys

print('Version Of Python: ' + sys.version)
print('Version Of Pandas: ' + pd.__version__)
print('Version Of Numpy: ' + np.version.version)

# Version Of Python: 3.10.9 | packaged by conda-forge | (main, Jan 11 2023, 15:15:40) [MSC v.1916 64 bit (AMD64)]
# Version Of Pandas: 1.5.3
# Version Of Numpy: 1.24.2

#%%
df = pd.DataFrame({'date_obj': ['2000-01-02', '2015-02-01', np.nan, '03.04.2015', '04.03.2009', np.nan, '5/6/2000', '6/5/2019', np.nan, '2016-07-08 00:00:00', '2007-08-07 00:00:00']}) 
df['date_str'] = df['date_obj'].astype('string')
df['date_str_noNA'] = df['date_str'].fillna('2002-02-20')
df['date_str_same_format'] = pd.Series('2123-01-10').repeat(len(df)).reset_index(drop=True).astype('string')

#%%
df['date_obj_to_datetime'] = pd.to_datetime(df['date_obj'])
df['date_str_to_datetime'] = pd.to_datetime(df['date_str'])
df['date_str_noNA_to_datetime'] = pd.to_datetime(df['date_str_noNA'])
df['date_str_same_format_to_datetime'] = pd.to_datetime(df['date_str_same_format'])

#%%
df['date_obj_astype'] = df['date_obj'].astype('datetime64[ns]')
df['date_str_same_format_astype'] = df['date_str_same_format'].astype('datetime64[ns]')

#%%
df['date_str_noNA_astype'] = df['date_str_noNA'].astype('datetime64[ns]')
    ### ValueError: Error parsing datetime string "03.04.2015" at position 2.
    ### "03.04.2015" is the first row with a different pattern from the beginning.

#%%
df['date_str_astype'] = df['date_str'].astype('datetime64[ns]')
    ### ValueError: Could not convert object to NumPy datetime.

#%%
print(df.dtypes.to_string(), '\n')
print(df.to_string())

[MarcoGorelli]

thanks for the report - you should use to_datetime and to_timedelta for such conversions

closing then

[nathanckuhn]

@MarcoGorelli , yes AND can "astype" be fixed to incorporate the improvements of "to_datetime"?
"astype" is a more generic function and should work just well as the more specific "to_datetime" function.
To me this is still a bug.
Thank you for your consideration!