Python advice: Portability of introspective function call
From the documentation:


  The resulting list is sorted alphabetically


As for the differences, I think you will have to check (and specifying in your answer is probably a good idea). There are clear differences between python 2 and 3, for example, __nonzero__ was renamed to __bool__.

I have never heard of any differences between implementations, but I can't find any references on this.

I don't think this has been used before in part because it will rarely save you any characters over doing something like:

F=str.capitalize
s='abc'
c=F(s)


You would need to use several different functions from dir() in order for this to be worth it.