title: Python zipfile module doesn't compress files
body: <p>I have a problem with compression in Python.
  I know I should call the ZIP_DEFLATED method when writing to make the zip file compressed, but it does not work for me.
  I have 3 PDF documents in the C:zip directory. 
  When I run the following code it works just fine:</p>
  
  <pre><code>import os,sys
  list = os.listdir('C:\zip')
  file = ZipFile('test.zip','w')
  for item in list:
      file.write(item)
  file.close()
  </code></pre>
  
  <p>It makes the test.zip file without the compression.
  When I change the fourth row to this:</p>
  
  <pre><code>file = ZipFile('test.zip','w', compression = ZIP_DEFLATED)
  </code></pre>
  
  <p>It also makes the test.zip file without the compression.
  I also tried to change the write method to give it the <em>compress</em>_ <em>type</em> argument:</p>
  
  <pre><code>file.write(item, compress_type = ZIP_DEFLATED)
  </code></pre>
  
  <p>But that doesn't work either.
  I use Python version 2.7.4 with Win7.
  I tired the code with another computer (same circumstances, Win7 and Python 2.7.4), and it made the test.zip file compressed just like it should.
  I know the zlib module should be available, when I run this:</p>
  
  <pre><code>import zlib
  </code></pre>
  
  <p>It doesn't return an error, also if there would be something wrong with the zlib module the code at the top should had return an error too, so I suspect that zlib isn't the problem.</p>