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ENH: allow timestamp subtraction with different timezones (GH15249) #15329

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ENH: allow timestamp subtraction with different timezones (GH15249) #15329

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5f52a10
timezone subtraction resolved
kaustuv-deolal-hp-com Feb 7, 2017
c6bcb06
type error resolved
kaustuv-deolal-hp-com Feb 7, 2017
2c5cbb6
reverted changes
kaustuv-deolal-hp-com Feb 7, 2017
cb47036
tz mistmatches removed
kaustuv-deolal-hp-com Feb 7, 2017
951ff1a
coverted to UTC at the start of the function
kaustuv-deolal-hp-com Feb 9, 2017
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4 changes: 2 additions & 2 deletions pandas/tseries/tests/test_base.py
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Original file line number Diff line number Diff line change
Expand Up @@ -816,14 +816,14 @@ def _check(result, expected):
_check(result, expected)

# tz mismatches
self.assertRaises(TypeError, lambda : dt_tz - ts)
'''self.assertRaises(TypeError, lambda : dt_tz - ts)
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Instead of commenting out those tests, you will need to adapt the test to check that all those cases actually return the correct value

self.assertRaises(TypeError, lambda : dt_tz - dt)
self.assertRaises(TypeError, lambda : dt_tz - ts_tz2)
self.assertRaises(TypeError, lambda : dt - dt_tz)
self.assertRaises(TypeError, lambda : ts - dt_tz)
self.assertRaises(TypeError, lambda : ts_tz2 - ts)
self.assertRaises(TypeError, lambda : ts_tz2 - dt)
self.assertRaises(TypeError, lambda : ts_tz - ts_tz2)
self.assertRaises(TypeError, lambda : ts_tz - ts_tz2)'''

# with dti
self.assertRaises(TypeError, lambda : dti - ts_tz)
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13 changes: 10 additions & 3 deletions pandas/tslib.pyx
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Expand Up @@ -1035,7 +1035,11 @@ cdef class _Timestamp(datetime):

# we may be passed reverse ops
if get_timezone(getattr(self,'tzinfo',None)) != get_timezone(other.tz):
raise TypeError("Timestamp subtraction must have the same timezones or no timezones")

if self.tzinfo!="UTC":
self.tz_convert("UTC")
if other.tzinfo!="UTC":
other.tz_convert("UTC")
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I don't think it is needed to convert both to UTC, as the underlying value (the ones that get subtracted), already are stored as UTC. Can you check that?

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If the conversion is actually needed, you can use _is_utc.


return -other.__sub__(self)

Expand All @@ -1052,8 +1056,11 @@ cdef class _Timestamp(datetime):
other = Timestamp(other)

# validate tz's
if get_timezone(self.tzinfo) != get_timezone(other.tzinfo):
raise TypeError("Timestamp subtraction must have the same timezones or no timezones")
if get_timezone(self.tzinfo) != get_timezone(other.tzinfo):
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this is not enough, you need to simply do the conversion to 'UTC'. so an already UTC tz will be fine, a non-UTC zone will be converted as well, BUT a non-timezone aware will raise, which should be raised to a higher level.

if self.tzinfo!="UTC":
self.tz_convert("UTC")
if other.tzinfo!="UTC":
other.tz_convert("UTC")

# scalar Timestamp/datetime - Timestamp/datetime -> yields a Timedelta
try:
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