进制之间互相转换代码

#--coding:utf8--


#file:baseconvert.py




BASE2 = "01"


BASE10 = "0123456789"


BASE16 = "0123456789ABCDEF"


BASE62 = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz"


BASE36 = "0123456789abcdefghijklmnopqrstuvwxyz"




def baseconvert(number,fromdigits,todigits):


""" converts a "number" between two bases of arbitrary digits




The input number is assumed to be a string of digits from the


fromdigits string (which is in order of smallest to largest


digit). The return value is a string of elements from todigits


(ordered in the same way). The input and output bases are


determined from the lengths of the digit strings. Negative


signs are passed through.




decimal to binary


>>> baseconvert(555,BASE10,BASE2)


'1000101011'




binary to decimal


>>> baseconvert('1000101011',BASE2,BASE10)


'555'




integer interpreted as binary and converted to decimal (!)


>>> baseconvert(1000101011,BASE2,BASE10)


'555'




base10 to base4


>>> baseconvert(99,BASE10,"0123")


'1203'




base4 to base5 (with alphabetic digits)


>>> baseconvert(1203,"0123","abcde")


'dee'




base5, alpha digits back to base 10


>>> baseconvert('dee',"abcde",BASE10)


'99'




decimal to a base that uses A-Z0-9a-z for its digits


>>> baseconvert(257938572394L,BASE10,BASE62)


'E78Lxik'




..convert back


>>> baseconvert('E78Lxik',BASE62,BASE10)


'257938572394'




binary to a base with words for digits (the function cannot convert this back)


>>> baseconvert('1101',BASE2,('Zero','One'))


'OneOneZeroOne'




"""




if str(number)[0]=='-':


number = str(number)[1:]


neg=1


else:


neg=0




# make an integer out of the number


x=long(0)


for digit in str(number):


x = x*len(fromdigits) + fromdigits.index(digit)




# create the result in base 'len(todigits)'


res=""


while x>0:


digit = x % len(todigits)


res = todigits[digit] + res


x /= len(todigits)


if neg:


res = "-"+res




return res