# first append the string with 0s to make its length a multiple of 8
while len(boolString) % 8 != 0:
    boolString += '0'

# write the string to the file byte by byte
i = 0
while i < len(boolString) / 8:
    byte = int(boolString[i*8 : (i+1)*8], 2)
    outputFile.write('%c' % byte)

    i += 1

b = bytearray([int(boolString[x:x+8], 2) for x in range(0, len(boolString), 8)])
outputFile.write(b)

bitstring.Bits(bin=boolString).tofile(outputFile)

while data > 0:
    data, byte = divmod(data, 0xff)
    file.write('%c' % byte)

import array

buffer = array.array('B')

i = 0
while i < len(boolString) / 8:
    byte = int(boolString[i*8 : (i+1)*8], 2)
    buffer.append(byte)
    i += 1

f = file(filename, 'wb')
buffer.tofile(f)
f.close()

class BitWriter:
    def __init__(self, f):
        self.acc = 0
        self.bcount = 0
        self.out = f

    def __del__(self):
        self.flush()

    def writebit(self, bit):
        if self.bcount == 8 :
            self.flush()
        if bit > 0:
            self.acc |= (1 << (7-self.bcount))
        self.bcount += 1

    def writebits(self, bits, n):
        while n > 0:
            self.writebit( bits & (1 << (n-1)) )
            n -= 1

    def flush(self):
        self.out.write(chr(self.acc))
        self.acc = 0
        self.bcount = 0

with open('outputFile', 'wb') as f:
    bw = BitWriter(f)
    bw.writebits(int(boolString,2), len(boolString))
    bw.flush()

def long_to_bytes(n, blocksize=0):
    """long_to_bytes(n:long, blocksize:int) : string
    Convert a long integer to a byte string.

    If optional blocksize is given and greater than zero, pad the front of the
    byte string with binary zeros so that the length is a multiple of
    blocksize.
    """
    # after much testing, this algorithm was deemed to be the fastest
    s = ''
    n = long(n)
    pack = struct.pack
    while n > 0:
        s = pack('>I', n & 0xffffffffL) + s
        n = n >> 32
    # strip off leading zeros
    for i in range(len(s)):
        if s[i] != '00':
            break
    else:
        # only happens when n == 0
        s = '00'
        i = 0
    s = s[i:]
    # add back some pad bytes.  this could be done more efficiently w.r.t. the
    # de-padding being done above, but sigh...
    if blocksize > 0 and len(s) % blocksize:
        s = (blocksize - len(s) % blocksize) * '00' + s
    return s

with open('outputFile', 'wb') as f:
    f.write(long_to_bytes(int(boolString, 2)))

import struct

p = struct.pack('????', True, False, True, False)
assert p == 'x01x00x01x00'
with open("out", "wb") as o:
    o.write(p)

$ ls -l out
-rw-r--r-- 1 lutz lutz 4 Okt  1 13:26 out
$ od out
0000000 000001 000001
000000

with open("out", "rb") as i:
    q = struct.unpack('????', i.read())
assert q == (True, False, True, False)