Timing Difference: insert vs. append & reverse
fakeaddress at nowhere.org
Fri Aug 6 10:35:20 CEST 2004
Tim Peters wrote:
> [Bryan Olson, on complicating the list object again, and 2.4's deque
>>But it breaks (efficient) indexing. Since we can have it all
>>like Perl, why not?
> As I said, the best Perl can do is O(1) amortized.
In fact, as both of us said.
> If you follow the link you gave last time and read to the bottom
> following the other links, you'll find that Perl lists had
> quadratic-time behavior under the steady-state queue pattern for a
> long time. That was eventually fixed -- or so they say. Small
> details are both tricky and vital.
Agreed. But those Perl wizards, misguided as they may be, are
> 2.4's deque implementation is
> obviously immune to "bad" patterns, steady-state queue or otherwise.
> Most immediately damning, adding another member to the list struct (to
> keep track of the "low bound") would increase the size of every list
> object by 8 bytes, on 32-bit boxes. Python lists are easy to spell,
> use and access, and some Python apps use millions of small lists.
> They wouldn't appreciate the RAM hit for a mostly-useless feature.
> Most Perl programmers seem to be so confused by Perl lists that they
> only use them when they have to, to shift function arguments in and
> out <0.6 wink>.
We must know different Perl programmers.
> That's a use case for lists Python doesn't have at
> You can pursue it if you want to, but with the 2.4 deque type I have
> no interest in messing more with the list type.
I'm talking about facilities and their implementations, not
people. True, when I pointed out that Perl nails this one, I
was kinda' thinking the comparison might motivate Pythoners to
pursue the same enhancement. It was certainly *not* meant to
deride anyone who contributed to implementing Python.
Is Tim the superior Pythoner? Duh. Does Python rock? Sure.
Is saving four-or-eight bytes more or less valuable than
providing efficient insert at both ends? With all due respect
to Python and the people who implemented it, Perl kicks on this
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