Script to generate MD5 checksum for a given file. Uses iterator implementation.

checksumGenerator.py

# checksumGenerator.py
# Python 2.7.6

"""
Script to generate MD5 checksum for a given file
Also see comparison of performance with iterator implementation
"""

import hashlib
import time

src_file = "md5/sample.xml"

def generate_md5(fname, chunk_size=4096):
    """
    Function which takes a file name and returns md5 checksum of the file
    """
    hash = hashlib.md5()
    with open(fname, "rb") as f:
        # Read the 1st block of the file
        chunk = f.read(chunk_size)
        # Keep reading the file until the end and update hash
        while chunk:
            hash.update(chunk)
            chunk = f.read(chunk_size)

    # Return the hex checksum
    return hash.hexdigest()


def read_file(fname, chunk_size=4096):
    """
    Iterator which reads file block by block
    """
    # Open the file in read binary mode
    with open(fname, "rb") as f:
        # Read the 1st block
        chunk = f.read(chunk_size)
        # Keep reading the file blocks till the end
        while chunk:
            yield chunk  # returns one block at a time
            chunk = f.read(chunk_size)


def generate_md5_with_iterator(fname):
    """
    using iterator to read file buffer chunks
    """
    hash = hashlib.md5()
    # Keeps looping till iterator runs
    for chunk in read_file(fname):
        hash.update(chunk)

    return hash.hexdigest()


if __name__ == "__main__":

    start1 = time.clock()
    checksum1 = generate_md5(src_file)
    end1 = time.clock()

    # Performancer of normal file read method
    duration1 = end1 - start1

    start2 = time.clock()
    # Generate checksum using iterator method
    checksum2 = generate_md5_with_iterator(src_file)
    end2 = time.clock()

    # Performance of file read using iterator method
    duration2 = end2 - start2

    print("checksum: {0}, Without iterator - timetaken: {1}".
        format(checksum1, duration1))
    print("checksum: {0}, With iterator - timetaken: {1}".
        format(checksum2, duration2))

    # Compare the performance
    if duration1 > duration2:
        print("Using iterator is faster by {}".
              format(duration1 - duration2))
    elif duration1 < duration2:
        print("Using iterator is slower by {}".
              format(duration2 - duration1))
    else:
        print("No significant impact in performance")