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Add test for GH 18523 and add _tz_compare() to compare timezone of DatetimeIndex #18596

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Add test for GH 18523 and add _tz_compare() to compare timezone of DatetimeIndex #18596

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Add test for GH 18523 and add _tz_compare() to compare timezone of Da…
MridulS Dec 1, 2017
259d6d8
Address comments on the PR
MridulS Dec 1, 2017
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19 changes: 17 additions & 2 deletions pandas/core/indexes/datetimes.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1127,6 +1127,21 @@ def join(self, other, how='left', level=None, return_indexers=False,
return Index.join(this, other, how=how, level=level,
return_indexers=return_indexers, sort=sort)

def _tz_compare(self, other):
"""
Compare time zones of DatetimeIndex.
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can you expound on the reason for this here (e.g. mention the directly comparing pytz of the same timezone is broken), but a str comparison is ok.


Parameters
----------
other: DatetimeIndex

Returns:
-------
compare : Boolean

"""
return str(self.tzinfo) == str(other.tzinfo)

def _maybe_utc_convert(self, other):
this = self
if isinstance(other, DatetimeIndex):
Expand All @@ -1138,7 +1153,7 @@ def _maybe_utc_convert(self, other):
raise TypeError('Cannot join tz-naive with tz-aware '
'DatetimeIndex')

if self.tz != other.tz:
if not self._tz_compare(other):
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can you also add for all the other cases of str(self.tz) != str(other) (or variants on this)

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The other places where pandas uses variants for str(self.tz) != str(other.tz) isn't particularly for DatetimeIndex. For example in test_timezones.py this is used to test the equality of Timestamp I guess we have to write a more general method which takes in any object with a .tz attribute and compare it. In that case which file should I put this method in?

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the right place to put this is in
pandas/_libs/tslibs/timezones.pyx

and just call it from where needed

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FYI - I added an additional instance of this in a commit that went in earlier today. Current location on master:

pandas/pandas/core/indexes/interval.py

Lines 242 to 243 in 288bf6e

elif (isinstance(left, ABCDatetimeIndex) and
str(left.tz) != str(right.tz)):

this = self.tz_convert('UTC')
other = other.tz_convert('UTC')
return this, other
Expand Down Expand Up @@ -1243,7 +1258,7 @@ def __iter__(self):

def _wrap_union_result(self, other, result):
name = self.name if self.name == other.name else None
if self.tz != other.tz:
if not self._tz_compare(other):
raise ValueError('Passed item and index have different timezone')
return self._simple_new(result, name=name, freq=None, tz=self.tz)

Expand Down
20 changes: 20 additions & 0 deletions pandas/tests/indexes/datetimes/test_construction.py
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Expand Up @@ -443,6 +443,26 @@ def test_000constructor_resolution(self):

assert idx.nanosecond[0] == t1.nanosecond

def test_concat(self):
idx1 = pd.date_range('2011-01-01', periods=3, freq='H',
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pls add the issue number as a comment

tz='Europe/Paris')
idx2 = pd.date_range(start=idx1[0], end=idx1[-1], freq='H')
df1 = pd.DataFrame({'a': [1, 2, 3]}, index=idx1)
df2 = pd.DataFrame({'b': [1, 2, 3]}, index=idx2)
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can you move this to pandas/tests/reshape/test_concat.py

res = pd.concat([df1, df2], axis=1)

assert str(res.index.tzinfo) == str(df1.index.tzinfo)
assert str(res.index.tzinfo) == str(df2.index.tzinfo)

idx3 = pd.date_range('2011-01-01', periods=3,
freq='H', tz='Asia/Tokyo')
df3 = pd.DataFrame({'b': [1, 2, 3]}, index=idx3)
res = pd.concat([df1, df3], axis=1)

assert str(res.index.tzinfo) == 'UTC'
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instead of this, can you construct the expected frame directly and use
tm.assert_frame_equal (same as above as well)

assert str(res.index.tzinfo) != str(df1.index.tzinfo)
assert str(res.index.tzinfo) != str(df3.index.tzinfo)


class TestTimeSeries(object):

Expand Down