title: Python broke, AttributeError: 'module' object has no attribute 'python_version'
body: <p>I am running 2.7 on Windows. I had no problems until yesterday when I tried to run a few jobs using the <code>multiprocessing</code> library, got a bunch of memory errors, and everything crashed. </p>
  
  <p>This is what happens when I try to run <code>pip</code>:</p>
  
  <pre><code>Traceback (most recent call last):
    File "C:\Python27\lib\runpy.py", line 162, in _run_module_as_ma
      "__main__", fname, loader, pkg_name)
    File "C:\Python27\lib\runpy.py", line 72, in _run_code
      exec code in run_globals
    File "C:\Python27\Scripts\pip.exe\__main__.py", line 5, in &lt;mod
    File "C:\Python27\lib\site-packages\pip\__init__.py", line 13,
      from pip.utils import get_installed_distributions, get_prog
    File "C:\Python27\lib\site-packages\pip\utils\__init__.py", lin
  e&gt;
      from pip._vendor import pkg_resources, six
    File "C:\Python27\lib\site-packages\pip\_vendor\__init__.py", l
  _module
      __import__(name)
    File "C:\Python27\lib\site-packages\pip\_vendor\pkg_resources\_
  ne 1316, in &lt;module&gt;
      class MarkerEvaluation(object):
    File "C:\Python27\lib\site-packages\pip\_vendor\pkg_resources\_
  ne 1320, in MarkerEvaluation
      'python_full_version': platform.python_version,
  AttributeError: 'module' object has no attribute 'python_version'
  </code></pre>
  
  <p>I get the same thing when I try to <code>import pandas</code> from the python shell. Oddly enough, when instead of import pandas i try to run <code>import pandas as pd</code>, I get this error:</p>
  
  <pre><code>In [3]: import pandas as pd
  cannot import name hashtable
  ------------------------------------------
  ImportError
  &lt;ipython-input-3-af55e7023913&gt; in &lt;module&gt;
  ----&gt; 1 import pandas as pd
  
  C:\Python27\lib\site-packages\pandas\__ini
        5
        6 try:
  ----&gt; 7     from . import hashtable, tslib
        8 except Exception:  # pragma: no co
        9     import sys
  
  ImportError: cannot import name hashtable
  </code></pre>
  
  <p>Any idea how I can fix this without completely reinstalling Python and all my libraries?</p>