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Viewing / Editing File: zlibdemo.py

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#! /usr/bin/env python

# Takes an optional filename, defaulting to this file itself.
# Reads the file and compresses the content using level 1 and level 9
# compression, printing a summary of the results.

import zlib, sys

def main():
    if len(sys.argv) > 1:
        filename = sys.argv[1]
    else:
        filename = sys.argv[0]
    print 'Reading', filename

    f = open(filename, 'rb')           # Get the data to compress
    s = f.read()
    f.close()

    # First, we'll compress the string in one step
    comptext = zlib.compress(s, 1)
    decomp = zlib.decompress(comptext)

    print '1-step compression: (level 1)'
    print '    Original:', len(s), 'Compressed:', len(comptext),
    print 'Uncompressed:', len(decomp)

    # Now, let's compress the string in stages; set chunk to work in smaller steps

    chunk = 256
    compressor = zlib.compressobj(9)
    decompressor = zlib.decompressobj()
    comptext = decomp = ''
    for i in range(0, len(s), chunk):
        comptext = comptext+compressor.compress(s[i:i+chunk])
    # Don't forget to call flush()!!
    comptext = comptext + compressor.flush()

    for i in range(0, len(comptext), chunk):
        decomp = decomp + decompressor.decompress(comptext[i:i+chunk])
    decomp=decomp+decompressor.flush()

    print 'Progressive compression (level 9):'
    print '    Original:', len(s), 'Compressed:', len(comptext),
    print 'Uncompressed:', len(decomp)

if __name__ == '__main__':
    main()

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