python module de/encoding bencoded data

bencode.py

#!/usr/bin/python2
# -*- coding: utf-8 -*-

def bencode(obj):
    if isinstance(obj, int):
        return "i" + str(obj) + "e"
    
    if isinstance(obj, str):
        return str(len(obj)) + ":" + obj
    
    if isinstance(obj, list):
        res = "l"
        for elem in obj:
            res += bencode(elem)
        return res + "e"
    
    if isinstance(obj, dict):
        res = "d"
        for key in sorted(obj.keys()):
            res += bencode(key) + bencode(obj[key])
        return res + "e"
    
    raise Exception, "Unknown object: %s"%repr(obj)

def bdecode(text):
    def bdecode_next(start):
        if text[start] == 'i':
            end = text.find('e', start)
            return int(text[start+1:end], 10), end + 1
        
        if text[start] == 'l':
            res = []
            start += 1
            while text[start] != 'e':
                elem, start = bdecode_next(start)
                res.append(elem)
            return res, start + 1
        
        if text[start] == 'd':
            res = {}
            start += 1
            while text[start] != 'e':
                key, start = bdecode_next(start)
                value, start = bdecode_next(start)
                res[key] = value
            return res, start + 1
        
        lenend = text.find(':', start)
        length = int(text[start:lenend], 10)
        end = lenend + length + 1
        return text[lenend+1:end], end
    return bdecode_next(0)[0]

assert bdecode("i42e") == 42
assert bdecode("3:foo") == 'foo'
assert bdecode("li42ei1337ee") == [42, 1337]
assert bdecode("li42eli42e3:baree") == [42, [42, 'bar']]
assert bdecode("d3:fooli42eee") == {'foo': [42]}
assert "i42e" == bencode(42)
assert "3:foo" == bencode('foo')
assert "li42ei1337ee" == bencode([42, 1337])
assert "li42eli42e3:baree" == bencode([42, [42, 'bar']])
assert "d3:fooli42eee" == bencode({'foo': [42]})

if __name__ == '__main__':
    import sys
    import getopt, json
    optlist, args = getopt.getopt(sys.argv[1:], 'de')
    
    if ('-e','') in optlist:
        from tempfile import NamedTemporaryFile
        import pprint
        import os
        
        if not len(args):
            raise Exception, "No file name given"
        inoutfile = open(args[0], "r")
        
        tmpfile = NamedTemporaryFile('w', delete=False)
        
        content = bdecode(inoutfile.read())
        pprint.pprint(content, tmpfile, 2)
        tmpfile.write('\n')
        tmpfile.close()
        inoutfile.close()
        
        os.system("vim %s"%(tmpfile.name))
        
        content = eval(open(tmpfile.name).read())
        inoutfile = open(args[0], "w")
        inoutfile.write(bencode(content))
        inoutfile.close()
        
        os.remove(tmpfile.name)
    else:
        if len(args) and args[0] != '-':
            filehandle = open(args[0], "r")
        else:
            filehandle = sys.stdin
        
        if ('-d','') in optlist:
            import pprint
            content = bdecode(filehandle.read())
            pprint.PrettyPrinter(indent=2).pprint(content)
        else:
            content = eval(filehandle.read())
            print bencode(content)

# vim: set ts=4 sw=4 et:

LICENSE

Copyright (c) 2015, PyroPeter <$nickname@$nickname.eu>

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

Thank you. This helped me decode a uTorrent .dat file to text.