def _extract(key, start, length):
    """Extract a bitstring from a string of binary digits, and return its
    numeric value."""
    k=key[start:start+length]
    return reduce(lambda x,y: x*2+48-ord(y), k, 0)
dataset/ETHPy150Open kuri65536/python-for-android/python3-alpha/python-libs/gdata/Crypto/Util/RFC1751.py/_extract/swapped operands of `-`