Validate bitcoin address python

## DJango field type for a Bitcoin Address#importrefromdjangoimportformsfromdjango.forms.utilimportValidationErrorfromCrypto.HashimportSHA256classBCAddressField(forms.CharField):default_error_messages= {'invalid': 'Invalid Bitcoin address.', }def__init__(self, *args, **kwargs):super(BCAddressField, self).__init__(*args, **kwargs)defclean(self, value):value=value.strip()ifre.match(r"[a-zA-Z1-9]{27,35}$", value) isNone:raiseValidationError(self.error_messages['invalid'])version=get_bcaddress_version(value)ifversionisNone:raiseValidationError(self.error_messages['invalid'])returnvalueimportmath__b58chars='123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'__b58base=len(__b58chars)defb58encode(v):""" encode v, which is a string of bytes, to base58. """long_value=0Lfor (i, c) inenumerate(v[::-1]):long_value+= (256**i) *ord(c)result=''whilelong_value>=__b58base:div, mod=divmod(long_value, __b58base)result=__b58chars[mod] +resultlong_value=divresult=__b58chars[long_value] +result# Bitcoin does a little leading-zero-compression: # leading 0-bytes in the input become leading-1s nPad=0forcinv:ifc=='\0': nPad+=1else: breakreturn (__b58chars[0]*nPad) +resultdefb58decode(v, length):""" decode v into a string of len bytes """long_value=0Lfor (i, c) inenumerate(v[::-1]):long_value+=__b58chars.find(c) * (__b58base**i)result=''whilelong_value>=256:div, mod=divmod(long_value, 256)result=chr(mod) +resultlong_value=divresult=chr(long_value) +resultnPad=0forcinv:ifc==__b58chars[0]: nPad+=1else: breakresult=chr(0)*nPad+resultiflengthisnotNoneandlen(result) !=length:returnNonereturnresultdefget_bcaddress_version(strAddress):""" Returns None if strAddress is invalid. Otherwise returns integer version of address. """addr=b58decode(strAddress,25)ifaddrisNone: returnNoneversion=addr[0]checksum=addr[-4:]vh160=addr[:-4] # Version plus hash160 is what is checksummed h3=SHA256.new(SHA256.new(vh160).digest()).digest()ifh3[0:4] ==checksum:returnord(version)returnNone