Joris Van den Bossche created ARROW-15883:
---------------------------------------------
Summary: [C++] Support for fractional seconds in strptime() for
ISO format?
Key: ARROW-15883
URL: https://issues.apache.org/jira/browse/ARROW-15883
Project: Apache Arrow
Issue Type: Improvement
Components: C++
Reporter: Joris Van den Bossche
Currently, we can't parse "our own" string representation of a timestamp array
with the timestamp parser {{strptime}}:
{code:python}
import datetime
import pyarrow as pa
import pyarrow.compute as pc
>>> pa.array([datetime.datetime(2022, 3, 5, 9)])
<pyarrow.lib.TimestampArray object at 0x7f00c1d53dc0>
[
2022-03-05 09:00:00.000000
]
# trying to parse the above representation as string
>>> pc.strptime(["2022-03-05 09:00:00.000000"], format="%Y-%m-%d %H:%M:%S",
>>> unit="us")
...
ArrowInvalid: Failed to parse string: '2022-03-05 09:00:00.000000' as a scalar
of type timestamp[us]
{code}
The reason for this is the fractional second part, so the following works:
{code:python}
>>> pc.strptime(["2022-03-05 09:00:00"], format="%Y-%m-%d %H:%M:%S", unit="us")
<pyarrow.lib.TimestampArray object at 0x7f00c1d6f940>
[
2022-03-05 09:00:00.000000
]
{code}
Now, I think the reason that this fails is because {{strptime}} only supports
parsing seconds as an integer
(https://man7.org/linux/man-pages/man3/strptime.3.html).
But, it creates a strange situation where the timestamp parser cannot parse the
representation we use for timestamps.
In addition, for CSV we have a custom ISO parser (used by default), so when
parsing the strings while reading a CSV file, the same string with fractional
seconds does work:
{code:python}
s = b"""a
2022-03-05 09:00:00.000000"""
from pyarrow import csv
>>> csv.read_csv(io.BytesIO(s))
pyarrow.Table
a: timestamp[ns]
----
a: [[2022-03-05 09:00:00.000000000]]
{code}
cc [~apitrou] [~rokm]
--
This message was sent by Atlassian Jira
(v8.20.1#820001)
