A simple unix calendar implementation in python

linux calendar

# -*- coding: utf-8 -*-
"""
Spyder Editor

This is a temporary script file.
"""
import os

def print_months(year, month):
    if year < 1900:
        print("CAN NOT PROCESS!!!")
        return
    start_year = 1900
    start_month = 1
    start_day = 1
    start_weekday = 1
    print_title(year, month)
    days = calculation(year, month, 1)
    day_of_week = days % 7
    for i in range(day_of_week):
        print('%3s' % '', end='')
    for i in range(month_days(year, month)):
        if ((i+1+day_of_week) % 7 == 0):
            print('%3s' % str(i+1), end='')
            print()
        else:
            print('%3s' % str(i+1), end='')
     
    
def print_title(year, month):
    months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 
              'August', 'September', 'October', 'November', 'December']
    month = months[month-1]
    month_len = len(month)
    center_content = month + " " + str(year)
    indent_len = (21 - len(center_content))/2
    indent_blank = ''
    for i in range(int(indent_len)):
        indent_blank += ' '
    print(indent_blank + center_content)
    print("%3s%3s%3s%3s%3s%3s%3s" % ("Su", "Mo", "Tu", "We", "Th", "Fr", "Sa"))
   
def is_prime_year(year):
    if year % 400 == 0 or year %4 == 0 and year % 100 != 0:
        return True
    else:
        return False
    
def month_days(year, month):
    is_prime = is_prime_year(year)
    if is_prime and month == 2:
        return 29
    elif not is_prime and month == 2:
        return 28;
    elif month in (1, 3, 5, 7, 8, 10, 12):
        return 31
    else:
        return 30

def year_days(year):
    if is_prime_year(year):
        return 366
    else:
        return 365


def calculation(year, month, day):
    days = 0
    for i in range(1900, year):
        days += year_days(i)
    for i in range(1, month):
        days += month_days(year, i)
    days += day
    return days
        
if __name__ == "__main__":
    print_months(2018, 2)