all Python 3calendarexception

calendar.IllegalMonthError

exceptions

Raised for a month number outside 1–12; a subclass of ValueError, and in newer versions of IndexError as well. The bad number is in the month attribute.

Syntax

except calendar.IllegalMonthError as e: e.month

Catch it as ValueError: that works on every version. Not every function raises it: weekday(2024, 13, 1) raises a plain ValueError from datetime, and month(2024, 13) failed with IndexError on 3.11 and early 3.12 releases, switching to IllegalMonthError only later. So except calendar.IllegalMonthError misses some bad-month errors.

Examples

import calendar
try:
    calendar.monthrange(2024, 13)
except ValueError as e:
    print(type(e).__name__, e.month)  # → IllegalMonthError 13

import calendar
try:
    calendar.weekday(2024, 13, 1)
except calendar.IllegalMonthError:
    print('IllegalMonthError')
except ValueError:
    print('ValueError')  # → ValueError — weekday() бросает обычный

See also

Common errors

Open in the full glossarydocs.python.orgReport an inaccuracy