[Python-3000] Default dict iterator should have been iteritems()

[Guido van Rossum]

On 9/4/07, Nicholas Bastin <nick.bastin at gmail.com> wrote:
> On 9/4/07, "Martin v. Löwis" <martin at v.loewis.de> wrote:
> > > (assuming d[x] is  O(log n))
> >
> > In Python, d[x] is typically considered to be O(1) (unlike in C++,
> > where it is O(log n)). Of course, with Python using a hashtable,
> > performance may decrease in the presence of collisions. In the
> > normal case, dict((x, d[x]) for x in d) will be O(n) in Python.
>
> Even if we suppose that d[x] is O(1) (and I don't have real data to
> say whether most uses of it actually conform to this, besides keyword
> argument passing), that still makes:
>
> [(x, d[x]) for x in d]
>
> O(2n), which is O(n), but only pedantically.  In the real world, 2n is
> still worse than n (and the hashtable means that it can devolve into
> O(n**2) in the worst case).

You shouldn't be using words whose meaning you don't understand.

> However, all that said, you'd probably
> never write the above line of code, and d.iteritems() will continue to
> suffice if there are concerns about 'for (k,v) in d' being materially
> different than 'if x in d'.

Since this is the python-3000 list, d.items() is what you're looking for.

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