title: Python treat files with uppercase and lowercase names the same
body: <p>I just found out this today:<br>
  If I have an existing file named a111, and I want to create a new file named A111 in the same directory with Python:  </p>
  
  <pre><code>f = file('A111', 'w')
  f.write('test')
  f.close()
  </code></pre>
  
  <p>It will overwrite my file a111 and there's no A111!!<br>
  How do I prevent this from happening?  </p>