Max limit of bytes in method update of Hashlib Python module -

i trying compute md5 hash of file function hashlib.md5() hashlib module.

so writed piece of code:

buffer = 128 f = open("c:\\file.tct", "rb") m = hashlib.md5()  while true:    p = f.read(buffer)    if len(p) != 0:       m.update(p)    else:       break print m.hexdigest() f.close() 

i noted function update faster if increase buffer variable value 64, 128, 256 , on. there upper limit cannot exceed? suppose might ram memory problem don't know.

big (≈2**40) chunk sizes lead memoryerror i.e., there no limit other available ram. on other hand bufsize limited 2**31-1 on machine:

import hashlib functools import partial  def md5(filename, chunksize=2**15, bufsize=-1):     m = hashlib.md5()     open(filename, 'rb', bufsize) f:         chunk in iter(partial(f.read, chunksize), b''):             m.update(chunk)     return m 

big chunksize can slow small one. measure it.

i find ≈10mb files 2**15 chunksize fastest files i've tested.