[python] AttributeError: Can only use .dt accessor with datetimelike values

Your problem here is that the dtype of 'Date' remained as str/object. You can use the parse_dates parameter when using read_csv

import pandas as pd
file = '/pathtocsv.csv'
df = pd.read_csv(file, sep = ',', parse_dates= [col],encoding='utf-8-sig', usecols= ['Date', 'ids'],)    
df['Month'] = df['Date'].dt.month

From the documentation for the parse_dates parameter

parse_dates : bool or list of int or names or list of lists or dict, default False

The behavior is as follows:

  • boolean. If True -> try parsing the index.
  • list of int or names. e.g. If [1, 2, 3] -> try parsing columns 1, 2, 3 each as a separate date column.
  • list of lists. e.g. If [[1, 3]] -> combine columns 1 and 3 and parse as a single date column.
  • dict, e.g. {‘foo’ : [1, 3]} -> parse columns 1, 3 as date and call result ‘foo’

If a column or index cannot be represented as an array of datetimes, say because of an unparseable value or a mixture of timezones, the column or index will be returned unaltered as an object data type. For non-standard datetime parsing, use pd.to_datetime after pd.read_csv. To parse an index or column with a mixture of timezones, specify date_parser to be a partially-applied pandas.to_datetime() with utc=True. See Parsing a CSV with mixed timezones for more.

Note: A fast-path exists for iso8601-formatted dates.

The relevant case for this question is the "list of int or names" one.

col is the columns index of 'Date' which parses as a separate date column.