1 #!/usr/bin/env python

     2 

     3 # Takes an optional filename, defaulting to this file itself.

     4 # Reads the file and compresses the content using level 1 and level 9

     5 # compression, printing a summary of the results.

     6 

     7 import zlib, sys

     8 

     9 def main():

    10     if len(sys.argv) > 1:

    11         filename = sys.argv[1]

    12     else:

    13         filename = sys.argv[0]

    14     print 'Reading', filename

    15 

    16     f = open(filename, 'rb')           # Get the data to compress

    17     s = f.read()

    18     f.close()

    19 

    20     # First, we'll compress the string in one step

    21     comptext = zlib.compress(s, 1)

    22     decomp = zlib.decompress(comptext)

    23 

    24     print '1-step compression: (level 1)'

    25     print '    Original:', len(s), 'Compressed:', len(comptext),

    26     print 'Uncompressed:', len(decomp)

    27 

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

    29 

    30     chunk = 256

    31     compressor = zlib.compressobj(9)

    32     decompressor = zlib.decompressobj()

    33     comptext = decomp = ''

    34     for i in range(0, len(s), chunk):

    35         comptext = comptext+compressor.compress(s[i:i+chunk])

    36     # Don't forget to call flush()!!

    37     comptext = comptext + compressor.flush()

    38 

    39     for i in range(0, len(comptext), chunk):

    40         decomp = decomp + decompressor.decompress(comptext[i:i+chunk])

    41     decomp=decomp+decompressor.flush()

    42 

    43     print 'Progressive compression (level 9):'

    44     print '    Original:', len(s), 'Compressed:', len(comptext),

    45     print 'Uncompressed:', len(decomp)

    46 

    47 if __name__ == '__main__':

    48     main()