Python dict.get's Default Value is Always Evaluated

This is a gotcha I ran across in some production code that is obvious in retrospect. I was profiling the code to find places where we were calling an_expensive_database_function and came across code like this:

def doit(*args, **kwargs):
     value = kwargs.get('key', an_expensive_database_function())

The original author probably assumed that …



I've always preferred maintainable code over clever code:

Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it. - Brian W. Kernighan

Kernighan had it right all those …