[python] How do I tell Python to convert integers into words

Code for this:

>>>def handel_upto_99(number):
predef={0:"zero",1:"one",2:"two",3:"three",4:"four",5:"five",6:"six",7:"seven",8:"eight",9:"nine",10:"ten",11:"eleven",12:"twelve",13:"thirteen",14:"fourteen",15:"fifteen",16:"sixteen",17:"seventeen",18:"eighteen",19:"nineteen",20:"twenty",30:"thirty",40:"fourty",50:"fifty",60:"sixty",70:"seventy",80:"eighty",90:"ninety",100:"hundred",100000:"lakh",10000000:"crore",1000000:"million",1000000000:"billion"}
if number in predef.keys():
    return predef[number]
else:
    return predef[(number/10)*10]+' '+predef[number%10]

>>>def return_bigdigit(number,devideby):
predef={0:"zero",1:"one",2:"two",3:"three",4:"four",5:"five",6:"six",7:"seven",8:"eight",9:"nine",10:"ten",11:"eleven",12:"twelve",13:"thirteen",14:"fourteen",15:"fifteen",16:"sixteen",17:"seventeen",18:"eighteen",19:"nineteen",20:"twenty",30:"thirty",40:"fourty",50:"fifty",60:"sixty",70:"seventy",80:"eighty",90:"ninety",100:"hundred",1000:"thousand",100000:"lakh",10000000:"crore",1000000:"million",1000000000:"billion"}
if devideby in predef.keys():
    return predef[number/devideby]+" "+predef[devideby]
else:
    devideby/=10
    return handel_upto_99(number/devideby)+" "+predef[devideby]

>>>def mainfunction(number):
dev={100:"hundred",1000:"thousand",100000:"lakh",10000000:"crore",1000000000:"billion"}
if number is 0:
    return "Zero"
if number<100:
    result=handel_upto_99(number)

else:
    result=""
    while number>=100:
        devideby=1
        length=len(str(number))
        for i in range(length-1):
            devideby*=10
        if number%devideby==0:
            if devideby in dev:
                return handel_upto_99(number/devideby)+" "+ dev[devideby]
            else:
                return handel_upto_99(number/(devideby/10))+" "+ dev[devideby/10]
        res=return_bigdigit(number,devideby)
        result=result+' '+res
        if devideby not in dev:
            number=number-((devideby/10)*(number/(devideby/10)))
        number=number-devideby*(number/devideby)

    if number <100:
        result = result + ' '+ handel_upto_99(number)
return result

result:

>>>mainfunction(12345)
' twelve thousand three hundred fourty five'
>>>mainfunction(2000)
'two thousand'