More Date Madness

date_to_str.py

def num_to_words(num):
    units = ["", "one", "two", "three", "four",  "five", 
    "six", "seven", "eight", "nine "]

    teens = ["", "eleven", "twelve", "thirteen",  "fourteen", 
        "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"]

    tens = ["", "ten", "twenty", "thirty", "forty",
        "fifty", "sixty", "seventy", "eighty", "ninety"]

    thousands = ["","thousand", "million",  "billion",  "trillion", 
        "quadrillion",  "quintillion",  "sextillion",  "septillion", "octillion", 
        "nonillion",  "decillion",  "undecillion",  "duodecillion",  "tredecillion", 
        "quattuordecillion",  "sexdecillion",  "septendecillion",  "octodecillion", 
        "novemdecillion",  "vigintillion "]
    words = []
    if num == 0:
        words.append("zero")
    else:
        numStr = "%d" % num
        numStrLen = len(numStr)
        groups = (numStrLen + 2) / 3
        numStr = numStr.zfill(groups * 3)
        for i in range(0, groups*3, 3):
            h = int(numStr[i])
            t = int(numStr[i+1])
            u = int(numStr[i+2])
            g = groups - (i / 3 + 1)
            
            if h >= 1:
                words.append(units[h])
                words.append("hundred")
                
            if t > 1:
                words.append(tens[t])
                if u >= 1:
                    words.append(units[u])
            elif t == 1:
                if u >= 1:
                    words.append(teens[u])
                else:
                    words.append(tens[t])
            else:
                if u >= 1:
                    words.append(units[u])
            
            if g >= 1 and (h + t + u) > 0:
                words.append(thousands[g])

    return words

def day_to_rank(day):
    try:
        day_to_values = {
            1: 'first',
            2: 'second',
            3: 'third',
            4: 'fourth',
            5: 'fifth',
            6: 'sixth',
            7: 'seventh',
            8: 'eighth',
            9: 'ninth',
            10: 'tenth',
            11: 'eleventh',
            12: 'twelfth',
            13: 'thirteenth',
            14: 'fourteenth',
            15: 'fifteenth',
            16: 'sixteenth',
            17: 'seventeenth',
            18: 'eighteenth',
            19: 'nineteenth',
            20: 'twentieth',
            30: 'thirtieth'
        }
        day = int(day)
        if day_to_values.get(day):
            return day_to_values.get(day)
        elif day > 20 and day < 30:
            return 'Twenty ' + day_to_values.get(day%10)
        elif day == 31:
            return 'Thirty ' + day_to_values.get(day%10)
    except:
        return ''
    return ''


def num_to_month(num):
    num_month_map = [
        '',
        'January',
        'February',
        'March',
        'April',
        'May',
        'June',
        'July',
        'August',
        'September',
        'October',
        'November',
        'December'
    ]
    if num<=12 and num >=1:
        return num_month_map[num]
    else:
        return ''

def isLeapYear(year):
    try:
        year = int(year)
        if (year % 4) == 0:
           if (year % 100) == 0:
               if (year % 400) == 0:
                   return True
               else:
                   return False
           else:
               return True
        else:
            return False
    except:
        return False

def num_days(mon, year):
    mon_num_days = [0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
    if isLeapYear(year) and mon == 2:
        return 29
    else:
        return mon_num_days[mon]

def validate_date(date):
    day = date.day
    month = date.month
    year = date.year
    if year <= 0:
        print "Year's value is invalid"
    if month <= 0 or month > 12:
        print "Month's value is invalid"
        exit()
    # validate for month and day max values
    if day <= 0 or day > num_days(month, year):
        print "Day's value is invalid for given month and year"
        exit()

    return

def print_formatted_date(date):
    day = date.day
    month = date.month
    year = date.year
    year_len = len(str(year))
    year = '0'*(4-year_len)+str(year)
    output = ''
    output += day_to_rank(int(day)).title()
    output += ' of ' + num_to_month(int(month)).title() + ', '
    output += ' '.join(num_to_words(int(year[0:2]))).title() + ' ' + ' '.join(num_to_words(int(year[2:4]))).title()
    print output


# Calling
print 'allowed date >= 01-01-0001'
date_input = raw_input('Enter Date: ')
date_input = date_input.strip()
from datetime import datetime
try:
    date_input = datetime.strptime(date_input, '%d-%m-%Y')
except ValueError:
    print 'invalid date'
    exit()
validate_date(date_input)
print_formatted_date(date_input)