How can I get a date that may not contain the month or the day?

Right now I only know how to break the date

date_n= '2022-12'
match_year = re.search(r'(?P<year_only>(?P<year>\d ))', date_n)
match_month = re.search(r'(?P<whole_date>(?P<year>\d )-(?P<month>\d ))', date_n)
match_day = re.search(r'(?P<whole_date>(?P<year>\d )-(?P<month>\d )-(?P<day>\d ))', date_n)

year = match_year.group('year_only')
month = match_month.group('month')
day = match_day.group('day')

Try and Except does not work.

CodePudding user response：

You should build patterns for each year, month and day and match them all in one expression (making month and day optional):

import re

date_n= '2022-12'
year_pattern = r"(?P<year>\d{4})"
month_pattern = r"(?:-(?P<month>\d{1,2}))"
day_pattern = r"(?:-(?P<day>\d{1,2}))"
match_date = re.search(rf'{year_pattern}(?:{month_pattern}{day_pattern}?)?', date_n)

year = match_date.group('year')
month = match_date.group('month')
day = match_date.group('day')