title: a concise form for concatenating a string, conditioned on some condition in python
body: <p>Many times I find myself writing code in the following form:</p>
  
  <pre><code>conditional_str = ''
  if condition:
      conditional_str = ' blah blah'
  
  output = 'my constant string' + conditional_str
  </code></pre>
  
  <p>I find it a bit cumbersome, and looking for a concise way of doing it.
  One way is to put this piece of code to a function.</p>
  
  <pre><code>output = conditional_str_concat(const_str, condition, conditional_str )
  </code></pre>
  
  <p>But I was wondering if there are better pythonic way of doing it.</p>