title: module 'itertools' has no attribute '__file__'
body: <p>I would like to use the itertools module, but I am not sure whether it is up and running. I found nothing in /usr/lib/python*. (2.7 and 3.5 are available, on my system and under a few VirtualEnv's). I found no duplicate question about this.</p>
  
  <p>I tried on my system:</p>
  
  <pre><code>alexandre@Martin-2:~$ python3
  Python 3.5.2 (default, Sep 14 2017, 22:51:06) 
  [GCC 5.4.0 20160609] on linux
  Type "help", "copyright", "credits" or "license" for more information.
  &gt;&gt;&gt; import sys
  &gt;&gt;&gt; sys.modules['itertools']
  &lt;module 'itertools' (built-in)&gt;
  &gt;&gt;&gt; import itertools
  &gt;&gt;&gt; itertools.__file__
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  AttributeError: module 'itertools' has no attribute '__file__'
  &gt;&gt;&gt; quit()
  </code></pre>
  
  <p>Any hint please?</p>