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pandas.DataFrame.tz_localize

DataFrame.tz_localize(tz, axis=0, level=None, copy=True, ambiguous='raise', nonexistent='raise')[source]

Localize tz-naive index of a Series or DataFrame to target time zone.

This operation localizes the Index. To localize the values in a timezone-naive Series, use Series.dt.tz_localize().

Parameters:
tz : string or pytz.timezone object
axis : the axis to localize
level : int, str, default None

If axis ia a MultiIndex, localize a specific level. Otherwise must be None

copy : boolean, default True

Also make a copy of the underlying data

ambiguous : ‘infer’, bool-ndarray, ‘NaT’, default ‘raise’

When clocks moved backward due to DST, ambiguous times may arise. For example in Central European Time (UTC+01), when going from 03:00 DST to 02:00 non-DST, 02:30:00 local time occurs both at 00:30:00 UTC and at 01:30:00 UTC. In such a situation, the ambiguous parameter dictates how ambiguous times should be handled.

  • ‘infer’ will attempt to infer fall dst-transition hours based on order
  • bool-ndarray where True signifies a DST time, False designates a non-DST time (note that this flag is only applicable for ambiguous times)
  • ‘NaT’ will return NaT where there are ambiguous times
  • ‘raise’ will raise an AmbiguousTimeError if there are ambiguous times
nonexistent : str, default ‘raise’

A nonexistent time does not exist in a particular timezone where clocks moved forward due to DST. Valid valuse are:

  • ‘shift_forward’ will shift the nonexistent time forward to the closest existing time
  • ‘shift_backward’ will shift the nonexistent time backward to the closest existing time
  • ‘NaT’ will return NaT where there are nonexistent times
  • timedelta objects will shift nonexistent times by the timedelta
  • ‘raise’ will raise an NonExistentTimeError if there are nonexistent times

New in version 0.24.0.
Returns:
Series or DataFrame

Same type as the input.
Raises:
TypeError

If the TimeSeries is tz-aware and tz is not None.

Examples

Localize local times:

>>> s = pd.Series([1],
... index=pd.DatetimeIndex(['2018-09-15 01:30:00']))
>>> s.tz_localize('CET')
2018-09-15 01:30:00+02:00    1
dtype: int64

Be careful with DST changes. When there is sequential data, pandas can infer the DST time:

>>> s = pd.Series(range(7), index=pd.DatetimeIndex([
... '2018-10-28 01:30:00',
... '2018-10-28 02:00:00',
... '2018-10-28 02:30:00',
... '2018-10-28 02:00:00',
... '2018-10-28 02:30:00',
... '2018-10-28 03:00:00',
... '2018-10-28 03:30:00']))
>>> s.tz_localize('CET', ambiguous='infer')
2018-10-28 01:30:00+02:00    0
2018-10-28 02:00:00+02:00    1
2018-10-28 02:30:00+02:00    2
2018-10-28 02:00:00+01:00    3
2018-10-28 02:30:00+01:00    4
2018-10-28 03:00:00+01:00    5
2018-10-28 03:30:00+01:00    6
dtype: int64

In some cases, inferring the DST is impossible. In such cases, you can pass an ndarray to the ambiguous parameter to set the DST explicitly

>>> s = pd.Series(range(3), index=pd.DatetimeIndex([
... '2018-10-28 01:20:00',
... '2018-10-28 02:36:00',
... '2018-10-28 03:46:00']))
>>> s.tz_localize('CET', ambiguous=np.array([True, True, False]))
2018-10-28 01:20:00+02:00    0
2018-10-28 02:36:00+02:00    1
2018-10-28 03:46:00+01:00    2
dtype: int64

If the DST transition causes nonexistent times, you can shift these dates forward or backwards with a timedelta object or ‘shift_forward’ or ‘shift_backwards’. >>> s = pd.Series(range(2), index=pd.DatetimeIndex([ … ‘2015-03-29 02:30:00’, … ‘2015-03-29 03:30:00’])) >>> s.tz_localize(‘Europe/Warsaw’, nonexistent=’shift_forward’) 2015-03-29 03:00:00+02:00 0 2015-03-29 03:30:00+02:00 1 dtype: int64 >>> s.tz_localize(‘Europe/Warsaw’, nonexistent=’shift_backward’) 2015-03-29 01:59:59.999999999+01:00 0 2015-03-29 03:30:00+02:00 1 dtype: int64 >>> s.tz_localize(‘Europe/Warsaw’, nonexistent=pd.Timedelta(‘1H’)) 2015-03-29 03:30:00+02:00 0 2015-03-29 03:30:00+02:00 1 dtype: int64

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