Unless I'm mistaken, the patch provides only half of the solution: the
stringToLong part, but not longToString.
I agree this feature is interesting, not for optimization but becomes it
avoids using clunky ways (long -> hex -> bin) to implement something simple.
However, perhaps making it part of either the binascii or the struct
module would allow more formatting choices (e.g. big-endian or
little-endian, fixed-length or not). For example in cryptography you
would want a byte string of a fixed size even if your 512-bit number
happens to have its 8 most significant bits set to zero.