AmbiguousTimeError in date_range using tz when start/end in dst transition.

[Safrone]

Code Sample

import datetime
import pytz
import pandas as pd
start = datetime.datetime(2018, 11, 1, 1, 0)
end = datetime.datetime(2018, 11, 4, 1, 0)
tz = pytz.timezone('America/New_York')

pd.date_range(start, end, tz=tz, ambiguous=True)

Traceback (most recent call last):
  File "/venv/lib/python3.5/site-packages/IPython/core/interactiveshell.py", line 3265, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "<ipython-input-40-6d5bf1272830>", line 1, in <module>
    pd.date_range(start, end, tz=self.timezone, ambiguous=False)
  File "/venv/lib/python3.5/site-packages/pandas/core/indexes/datetimes.py", line 2749, in date_range
    closed=closed, **kwargs)
  File "/venv/lib/python3.5/site-packages/pandas/core/indexes/datetimes.py", line 381, in __new__
    ambiguous=ambiguous)
  File "/venv/lib/python3.5/site-packages/pandas/core/indexes/datetimes.py", line 587, in _generate
    end = end.tz_localize(tz).asm8
  File "pandas/_libs/tslibs/timestamps.pyx", line 903, in pandas._libs.tslibs.timestamps.Timestamp.tz_localize
  File "pandas/_libs/tslibs/conversion.pyx", line 963, in pandas._libs.tslibs.conversion.tz_localize_to_utc
pytz.exceptions.AmbiguousTimeError: Cannot infer dst time from '2018-11-04 01:00:00', try using the 'ambiguous' argument

Problem description

pd.date_range does not honor the ambiguous keyword

Expected Output

DatetimeIndex(['2018-11-01 01:00:00-04:00', '2018-11-02 01:00:00-04:00',
               '2018-11-03 01:00:00-04:00', '2018-11-04 01:00:00-04:00'],
              dtype='datetime64[ns, America/New_York]', freq='D')

or

DatetimeIndex(['2018-11-01 01:00:00-04:00', '2018-11-02 01:00:00-04:00',
               '2018-11-03 01:00:00-04:00', '2018-11-04 01:00:00-05:00'],
              dtype='datetime64[ns, America/New_York]', freq='D')

depending on the truth value of ambiguous

Output of pd.show_versions()

INSTALLED VERSIONS

commit: None
python: 3.5.6.final.0
python-bits: 64
OS: Linux
OS-release: 4.15.0-38-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8
pandas: 0.23.4
pytest: None
pip: 10.0.1
setuptools: 39.1.0
Cython: None
numpy: 1.13.3
scipy: 1.1.0
pyarrow: None
xarray: None
IPython: 7.0.1
sphinx: None
patsy: None
dateutil: 2.6.0
pytz: 2018.5
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: 2.2.2
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: 4.2.5
bs4: 4.6.3
html5lib: None
sqlalchemy: None
pymysql: None
psycopg2: 2.7.5 (dt dec pq3 ext lo64)
jinja2: 2.10
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None

[gfyoung]

cc @mroeschke

I believe we might have fixed this in #22647?

@Safrone : Thanks for filing this! Can you installing the master branch an re-running your code?

[Safrone]

With the latest branch:

import datetime
import pytz
import pandas as pd
print(pd.__version__)

0.24.0.dev0+917.gf0877eccc

start = datetime.datetime(2018, 11, 1, 1, 0)
end = datetime.datetime(2018, 11, 4, 1, 0)
tz = pytz.timezone('America/New_York')
dr = pd.date_range(start, end, tz=tz, ambiguous=True)
print(dr)

DatetimeIndex(['2018-11-01 01:00:00-04:00', '2018-11-02 01:00:00-04:00',
               '2018-11-03 01:00:00-04:00', '2018-11-04 01:00:00-04:00'],
              dtype='datetime64[ns, America/New_York]', freq='D')

Thanks!

[mroeschke]

Glad it's working for you on master (I believe this was fixed recently). This will be apart of the v0.24.0 release.