Python Workshop the Edge 2007

import struct
struct.pack("i", 100000) #-> '\xa0\x86\x01\x00'

# という感じのものを作れということでしょうか？

from struct import *

# をstolen_struct.pyとして保存すれば、

import stolen_struct
stolen_struct.pack("i", 100000)

# と使える。

# 速度とかは考慮していません。

# my_module.py

_n = 256

def int_to_bits(i):
    def f(i):
        if i < 0:
            signbit = 1
            i = -i
        else:
            signbit = 0
        while i:
            yield i % _n
            i //= _n
        yield signbit

    return "".join(chr(n) for n in f(i))

def bits_to_int(bits):
    result = 0
    for i in xrange(len(bits) - 1):
        result += ord(bits[i]) * (_n ** i)
    if ord(bits[-1]):
        result = -result
    return result

# test

import my_module as m

def main():
    for i in xrange(-1000, 1000 + 1):
        bits = m.int_to_bits(i)
        print i, repr(bits)
        assert m.bits_to_int(bits) == i

if __name__ == '__main__':
    main()

import sys

def byte2bits(i):
    """
    convert byte as bit list.

    >>> byte2bits(10)
    [0, 0, 0, 0, 1, 0, 1, 0]
    """
    return [(i >> j) & 0x01 for j in reversed(range(8))]

_BYTE_TO_BITS = [byte2bits(i) for i in xrange(0x100)]

def int2bits(i):
    """
    convert integer as bit list.

    >>> int2bits(49015)
    [1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1]
    """
    def f(x):
        while x > 0:
            yield _BYTE_TO_BITS[x & 0xff]
            x >>= 8
    return sum(reversed(list(f(i))), [])
    
def bits2int(bits):
    """
    convert bit list as integer

    >>> bits2int([0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 0])
    29556
    """
    return reduce(lambda r, x: r << 1 | x, bits, 0)

def _test():
    import doctest
    doctest.testmod()

if __name__ == '__main__':
    _test()

#素直に
def int2bits(i):
    b = ''
    l = len(str(i))
    idx = 0
    while True:
        b += str((i)&1)
        i >>= 1
        if i == 0:
            break
        idx += 1
    return b[::-1]

def bits2int(b):
    i = 0
    l = len(b)
    for idx,v in enumerate(b):
        i += (int(v)<<(l-(idx+1)))
    return i

def main():
    b = '1111111111111111101101'
    i =  bits2int(b)
    print i
    b = int2bits(i)
    print b
    
    i = 1234567890
    b = int2bits(i)
    print b
    i = bits2int(b)
    print i

if __name__ == '__main__':
    main()

ぎゃあ、
int2bits のl = len(str(i))は不要でした。