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BUG: pd.to_datetime(infer_datetime_format=True) drops timezone #42068

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Merged
merged 12 commits into from
Sep 14, 2021
Merged

BUG: pd.to_datetime(infer_datetime_format=True) drops timezone #42068

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2b6e9f6
fix to_datetime with infer_datetime_format drop tz
i-aki-y Jun 17, 2021
09a5108
Fix fix reference issue number
i-aki-y Jun 17, 2021
1886b22
make guess_datetime_format parse more timezon pattern
i-aki-y Jun 19, 2021
309b5d9
make guess_datetime_format can parse offset with separator
i-aki-y Jun 23, 2021
7198d51
remove redundant parentheses and separator check
i-aki-y Jun 24, 2021
f42be84
Simplify timezone offset handling.
i-aki-y Jun 30, 2021
44dbf67
Merge branch 'master' into fix-infer_datetime_format-drop-timezone
i-aki-y Aug 7, 2021
a031e39
fix whatsnew entry
i-aki-y Aug 7, 2021
8033fe7
Merge branch 'master' into fix-infer_datetime_format-drop-timezone
jreback Sep 10, 2021
267b971
Merge branch 'master' into fix-infer_datetime_format-drop-timezone
i-aki-y Sep 13, 2021
a5136ed
Add to_datetime(,infer_datetime_format=True) bench
i-aki-y Sep 14, 2021
0538167
Fix style
i-aki-y Sep 14, 2021
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4 changes: 4 additions & 0 deletions pandas/_libs/tslibs/parsing.pyx
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Original file line number Diff line number Diff line change
Expand Up @@ -825,6 +825,10 @@ def format_is_iso(f: str) -> bint:
iso_template = '%Y{date_sep}%m{date_sep}%d{time_sep}%H:%M:%S.%f'.format
excluded_formats = ['%Y%m%d', '%Y%m', '%Y']

if (f is not None) and (f[-2:] in ["SZ", "fZ"]):
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As mentioned in my other comment, shouldn't %z be checked in the iso_template?

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I agree, I will revise my PR.

# remove last 'Z'
f = f[:-1]

for date_sep in [' ', '/', '\\', '-', '.', '']:
for time_sep in [' ', 'T']:
if (iso_template(date_sep=date_sep,
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17 changes: 17 additions & 0 deletions pandas/tests/tools/test_to_datetime.py
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Expand Up @@ -1941,6 +1941,23 @@ def test_infer_datetime_format_tz_name(self, tz_name, offset):
)
tm.assert_series_equal(result, expected)

@pytest.mark.parametrize(
"ts,zero_tz,is_utc",
[
("2019-02-02 08:07:13", "Z", True),
("2019-02-02 08:07:13", "", False),
("2019-02-02 08:07:13.012345", "Z", True),
("2019-02-02 08:07:13.012345", "", False),
],
)
def test_infer_datetime_format_zero_tz(self, ts, zero_tz, is_utc):
# GH 41047
s = Series([ts + zero_tz])
result = to_datetime(s, infer_datetime_format=True)
tz = pytz.utc if is_utc else None
expected = Series([Timestamp(ts, tz=tz)])
tm.assert_series_equal(result, expected)

@pytest.mark.parametrize("cache", [True, False])
def test_to_datetime_iso8601_noleading_0s(self, cache):
# GH 11871
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26 changes: 26 additions & 0 deletions pandas/tests/tslibs/test_parsing.py
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Expand Up @@ -226,3 +226,29 @@ def test_parse_time_string_check_instance_type_raise_exception():
result = parse_time_string("2019")
expected = (datetime(2019, 1, 1), "year")
assert result == expected


@pytest.mark.parametrize(
"fmt,expected",
[
("%Y %m %d %H:%M:%S", True),
("%Y/%m/%d %H:%M:%S", True),
(r"%Y\%m\%d %H:%M:%S", True),
("%Y-%m-%d %H:%M:%S", True),
("%Y.%m.%d %H:%M:%S", True),
("%Y%m%d %H:%M:%S", True),
("%Y-%m-%dT%H:%M:%S", True),
("%Y-%m-%dT%H:%M:%SZ", True),
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This doesn't appear like a valid strftime directive. To parse Z, I think %z needs to be used e.g.

In [9]: datetime.datetime.strptime("2020-05-01T18:04:03Z", "%Y-%m-%dT%H:%M:%S%z")
Out[9]: datetime.datetime(2020, 5, 1, 18, 4, 3, tzinfo=datetime.timezone.utc)

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@i-aki-y i-aki-y Jun 18, 2021 •
edited
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Thank you for your comment.
My fix was done to fit the output of guess_datetime_format.

ex.

In [1]: from pandas._libs.tslibs.parsing import guess_datetime_format
   ...: guess_datetime_format('2020-05-01T18:04:03Z')
Out[1]: '%Y-%m-%dT%H:%M:%SZ'

But as you said, the format string like "%SZ" should be "%S%z"
So now I guess the guess_datetime_format function also has some bugs.

("%Y-%m-%dT%H:%M:%S.%f", True),
("%Y-%m-%dT%H:%M:%S.%fZ", True),
("%Y%m%d", False),
("%Y%m", False),
("%Y", False),
("%Y-%m-%d", True),
("%Y-%m", True),
],
)
def test_is_iso_format(fmt, expected):
# see gh-41047
result = parsing.format_is_iso(fmt)
assert result == expected