Hashing a file in Python

Question

I want python to read to the EOF so I can get an appropriate hash, whether it is sha1 or md5. Please help. Here is what I have so far:

import hashlib

inputF         


        

Answer 1

For the correct and efficient computation of the hash value of a file (in Python 3):

• Open the file in binary mode (i.e. add 'b' to the filemode) to avoid character encoding and line-ending conversion issues.
• Don't read the complete file into memory, since that is a waste of memory. Instead, sequentially read it block by block and update the hash for each block.
• Eliminate double buffering, i.e. don't use buffered IO, because we already use an optimal block size.
• Use readinto() to avoid buffer churning.

Example:

import hashlib

def sha256sum(filename):
    h  = hashlib.sha256()
    b  = bytearray(128*1024)
    mv = memoryview(b)
    with open(filename, 'rb', buffering=0) as f:
        for n in iter(lambda : f.readinto(mv), 0):
            h.update(mv[:n])
    return h.hexdigest()