Demo/zlib/zlibdemo.py

   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()