This was a test I had some years ago, I used it as motivation to learn Python basics.

calendar.py

#!/usr/bin/env python
#-*- coding:utf-8 -*-
"""Prints a calendar by month, the user provides the year in a four digit format
and the month.

Exported Classes:
MonthCalendar - Formats and does the calculations for the CLI output of the
    calendar
Cli - Recieves the data input and validates it

Author - Lecksfrawen <[email protected]>
Date: Tue Apr 13 16:23:55 CDT 2010

"""

import calendar

class MonthCalendar:
    """ Prints the title of the desired month calendar, the week order starts
    from Sunday. """

    def __init__(self, year = None, month = None):
        self.months = [
            'January',
            'February',
            'March',
            'April',
            'May',
            'June',
            'July',
            'August',
            'September',
            'October',
            'November',
            'December'
            ]
        self.year = int(year)
        self.month = int(month)
        self.weeksday = calendar.setfirstweekday(6)


    def cal_header(self):
        month_year = "%15s %3d " %(self.months[self.month-1], self.year)
        return month_year


    def week_order(self):
        week_order = "%3s %3s %3s %3s %3s %3s %3s" %("Su","Mo","Tu","We","Th","Fr","Sa")
        return week_order


    def create_calendar(self):
        month = calendar.monthcalendar(self.year, self.month)
        nweeks = len(month)
        """ Knowing the number of weeks in the month, we can create a for loop
        which counts through a range() from 0 to the number of weeks. As it does,
        it will print out the rest of the calendar. """
        output_cal = ""

        for w in range(0,nweeks):
            week = month[w]
            output_cal += "\n"
            for x in xrange(0,7):
                day = week[x]

                if day == 0:
                    empty_day = ' '
                    output_cal += '%3s ' %(empty_day)

                else:
                    output_cal += '%3s ' %(day)
            output_cal += "\n"
        return output_cal


class Cli:
    """ Provides de input interface """

    def __init__(self):
        pass

    def get_year(self):
        """ Obtains the year from the cmd """
        error = True
        while error:
            sel_year = raw_input('Introduce el año: ')
            if sel_year.isdigit():
                sel_year = int(sel_year)
                if 1899 < sel_year < 3000:
                    error = False
                else:
                    print "\nEl año no puede ser menor a 1900 o mayor a 2999.\n \
                     Introduzca un año valido.\n"
            else:
                print "Porfavor dame un entero, no un string"
        return sel_year


    def get_month(self):
        """ Obtains the month from the cmd """
        error = True
        while error:
            sel_month = raw_input('Introduce el mes: ')
            if sel_month.isdigit():
                sel_month = int(sel_month)
                if 0 < sel_month and sel_month < 13:
                    print ""
                    error = False
                else:
                    print "\nEl mes no puede ser menor a 01 o mayor que 12.\n \
                     Introduzca un mes valido.\n"
            else:
                print "Porfavor dame un entero, no un string"
        return sel_month


def main():
    """ Asks for the month and year and proceeds to print the calendar
    for that specific month.
    """
    myCli = Cli()
    year = myCli.get_year()
    month = myCli.get_month()
    myMonthCal = MonthCalendar(year, month)

    print myMonthCal.cal_header()
    print myMonthCal.week_order()
    print myMonthCal.create_calendar()


if __name__ == '__main__':
    main()