pyPrintMonthCalendar

# Print a calendar for a chosen year and month, highlighting a chosen day

month_days = [0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
month_names = ["", "January", "February", "March", "April", "May", "June",
               "July", "August", "September", "October", "November", "December"]

def get_int(prompt, low, high):
    # A user function to get a valid integer within a specified range
    while True:
        try:
            num = int(input(prompt))
            if low <= num <= high:
                return num
            raise Exception()
        except:
            print("Invalid input. Try again\n")

year = get_int("Enter the year: (1901 to 2099): ", 1901, 2099)
month_days[2] = [29, 28, 28, 28][year % 4]              # Feb has 29 days in a leap year, otherwise 28

month = get_int("Choose a month: ", 1, 12)
day = get_int("Choose a day from the given month: ", 1, month_days[month])

work = 2 + (year - 1901) * 365 + (year - 1901) // 4     # 365 days per year +1 per leap, start=Tues 1-1-1901
month1st = 1 + (work + sum(month_days[:month])) % 7     # Day-of-week of 1st of month, base 1

heading = month_names[month] + " " + str(year)
print(f"\n{heading:^29}")                   # print month and year, centred on line
print(" Sun Mon Tue Wed Thu Fri Sat")       # print day abbreviations
dayno = 2 - month1st                        # go back to the last Sunday before or equal to the 1st of this month
while dayno <= month_days[month]:
    for _ in range(7):                      # 7 days per print line
        if dayno < 1 or dayno > month_days[month]:  # print spaces before month start and after month end
            print("    ", end="")
        else:
            work = ['', '*'][dayno == day] + str(dayno)     # prefix chosen day with "*"
            print(f"{work:>4}", end='')                     # print day number, right aligned
        dayno += 1
    print()