I'm importing data into pandas and want to remove any timezones – if they're present in the data. If the data has a time zone, the following code works successfully:

col = "my_date_column"
df[col] = pd.to_datetime(df[col]).dt.tz_localize(None) # We don't want timezones...

If the data does not contain a timezone, I'd like to use the following code:

df[col] = pd.to_datetime(df[col])

My issue is that I'm not sure how to test for timezone in the datetime object / series.

Assuming you have a column of type datetime, you can check the tzinfo of each timestamp in the column. It's basically described here (although this is not specific to pytz). Ex:

import pandas as pd# example series:
s = pd.Series([pd.Timestamp("2020-06-06").tz_localize("Europe/Berlin"), # tzinfo definedpd.Timestamp("2020-06-07") # tzinfo is None])# s
# 0    2020-06-06 00:00:00+02:00
# 1          2020-06-07 00:00:00
# dtype: object# now find a mask which is True where the timestamp has a timezone:
has_tz = s.apply(lambda t: t.tzinfo is not None)# has_tz
# 0     True
# 1    False
# dtype: bool