Valid month, day and year

Valid.py

# Validation functions for month, day, and year


months = ['January',
          'February',
          'March',
          'April',
          'May',
          'June',
          'July',
          'August',
          'September',
          'October',
          'November',
          'December']
          
def valid_month(month):
    if (month.lower()).capitalize() in months:
        return month.capitalize()
    else:
        return None
        
        
def valid_day(day):
    if day.isdigit():
        if int(day) <= 31 and int(day) > 0:
            return int(day)

# valid_day('0') => None    
# valid_day('1') => 1
# valid_day('15') => 15
# valid_day('500') => None

def valid_year(year):
    if year.isdigit():
        year = int(year)
        if year >= 1900 and year <= 2020:
            return year

# valid_year('0') => None    
# valid_year('-11') => None
# valid_year('1950') => 1950
# valid_year('2000') => 2000