title: Python equivalent of c++ find_if
body: <p>Is there a built-in python equivalent of <code>std::find_if</code> to find the first element of a list for which a given condition is <code>true</code>? In other words, something like the <code>index()</code> function of a list, but with an arbitrary unary predicate rather than just a test for equality. </p>
  
  <p>I don't want to use list comprehension, because the specific predicate I have in mind is somewhat expensive to compute. </p>