title: Is there a PEP484 type hint for 'character'?
body: <p>In short: is there a Python type hint for 'character', representing a length-one <code>str</code> but not using the type hint <code>str</code>?</p>
  
  <p>I saw <code>chr</code> used recently for this purpose, and other than intuition I can't find anything to prove or disprove that this is appropriate. It's apparently valid Python syntax. By example,</p>
  
  <pre><code>&gt;&gt;&gt; def foo(c: chr):
  ...   pass
  ... 
  &gt;&gt;&gt; foo('a')
  &gt;&gt;&gt; 
  </code></pre>
  
  <p>This raises more questions than it answers: is <code>chr</code> considered a valid type hint because it's a callable, and all types are "callable" by their constructors? Seems no - some quick experiments show that Python will in fact accept any defined symbol as a type hint, regardless of whether it makes sense.</p>