using `bytes` in python 2 and 3

Question

I am trying to write a Bitcoin address validator, and I am trying to make it work with Python 2 and 3.

import codecs
from hashlib import sha256

digits58 = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'

def to_bytes(n, length):
    s = '%x' % n
    s = s.rjust(length*2, '0')
    s = codecs.decode(bytes(s, 'UTF-8'), 'hex_codec')
    return s

def decode_base58(bc, length):
    n = 0
    for char in bc:
        n = n * 58 + digits58.index(char)
    return to_bytes(n, length)

def check_bc(bc):
    bcbytes = decode_base58(bc, 25)
    return bcbytes[-4:] == sha256(sha256(bcbytes[:-4]).digest()).digest()[:4]

if __name__ == '__main__':
    print(check_bc('1111111111111111111114oLvT2'))

This code should run and print True. Instead, it errors on this line in Python 2:

s = codecs.decode(bytes(s, 'UTF-8'), 'hex_codec')

Error:

TypeError: str() takes at most 1 argument (2 given)

If I remove the 'UTF-8' part, it breaks in Python 3 instead. If I remove the call to bytes altogether, it breaks in Python 3.

@MarkRansom See tag wiki.

Nick ODell
– Nick ODell

2023-05-28 04:28:39 +00:00
Commented May 28, 2023 at 4:28 — Nick ODell
– Nick ODell, Commented May 28, 2023 at 4:28

DSM · Accepted Answer · 2014-11-07 04:51:39Z

5

IIUC, instead of calling bytes, you can encode directly:

s = codecs.decode(s.encode("UTF-8"), 'hex_codec')

which gives

dsm@notebook:~/coding$ python2.7 bitcoin.py
True
dsm@notebook:~/coding$ python3.4 bitcoin.py
True

answered Nov 7, 2014 at 4:51

DSM

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