[Python-Dev] {}.getitem() (was Re: PEP-0218)

[Guido van Rossum]

> > > BTW, I don't get the inspiration for the "first" part in those
> > > names... it makes you think that there's an order to dictionary
> > > items when in reality there isn't.
> > 
> > Actually there is -- the (arbitrary) order revealed by .keys().
> 
> Hmm, but this can change if you modify the dictionary inside the
> loop or if you modify the dictionary from some other thread.

Let me explain.  When Moshe first proposed a .key() method, I was a
bit confused.  I thought he wanted a way to get to the i-th key (which
can't be done in O(1) time).  Then I thought he wanted a way to get a
random key.  Finally I realized that all he wanted was *a* key, and
the first key in the hash table would work fine.  Since that's also
the first key of .keys(), I figured "first" was an appropriate
qualification.  Sure, it's not guaranteed to remain the first key, but
neither is the first item in a list.

That said, getting rid of the first*() suite and adding popitem()
instead sounds attractive...

--Guido van Rossum (home page: http://www.python.org/~guido/)