Do you have that one thing that you have to constantly look up?

In python, to replace elements of a string, there are two operators.  One is a strictly linear search, the other uses regular expressions.  The regexp call to replace part of a string with another string is sub, and the string call to replace a part of a string with another string is replace.

I get these backward all the flamin' time, and it drives me insane.  I use both of these every day, why the Hell can't I remember which is which?