Put code in a main() function; loosen up the spacing to match current code style

Demo/zlib/zlibdemo.py

 #!/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
-if len(sys.argv)>1: filename=sys.argv[1]
-else: filename='zlibdemo.py'
-print 'Reading', filename
-f=open(filename, 'r')           # 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])
-comptext=comptext+compressor.flush()    # Don't forget to call 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)
+
+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()