Rant (was Re: x*x if x>10
Gary Herron
gherron at islandtraining.com
Sun Jul 27 12:28:28 EDT 2008
DaveM wrote:
> On Sun, 27 Jul 2008 16:57:14 +0200, "Diez B. Roggisch" <deets at nospam.web.de>
> wrote:
>
>
>> Marc 'BlackJack' Rintsch schrieb:
>>
>>> On Sun, 27 Jul 2008 16:41:19 +0200, Diez B. Roggisch wrote:
>>>
>>>
>>>> DaveM schrieb:
>>>>
>>>>> Getting back to the list concatenation, I finally found the itertools.chain
>>>>> command which is the most compact and fastest (or second fastest by a
>>>>> trivial amount, I can't remember which). Along the way, I must have
>>>>> tried/used half a dozen methods, ...which brings me back my initial PERL
>>>>> comment. There's more than one way to do it in Python, too.
>>>>>
>
>
>>>> But I *do* know that taking the python zen literally is fruitless.
>>>>
>
>
>>> I think it should be taken more literally than the wrong reduction to
>>> "there should be only one way". People tend to forget "obvious" and
>>> "preferably" all the time.
>>>
>
>
>> Good point. The OP found the obvious way of extending. I wonder what his
>> reasons were to abandon it.
>>
>
> You'll have guessed, I'm sure, that I'm not a professional programmer. This
> was the third rewrite of a program to match candidate groups to examiners on
> a three day course I run, necessitated on this occasion by a change in the
> structure of the course. I originally learnt python as I wrote, and some of
> the early code was ugly and verbose, so once the current rewrite was working
> I took the opportunity to tidy the code up and document it (yes, I know, but
> as I said, I'm an amateur). The list concatenation was an itch I couldn't
> scratch:
>
> temp = []
> for value in sessexam.values():
> temp.extend(value)
> c_exam = [name for name in set(temp)] #See what I mean about verbose?
> c_exam.sort()
> return c_exam
>
> Six lines just didn't feel like it ought to be the best way to do something
> so simple. I liked the attempt below better, but was foolish enough to time
> it, so that was the end of that.
>
> return sorted(list(set(reduce(lambda x, y: x+y, sessexam.values()))))
>
> The current version (below) is a compromise, but I still feel there _ought_
> to be a simple one word command to join multiple lists.
>
> a = list(set(itertools.chain(*sessexam.values())))
> a.sort() #As I write I'm wondering if I really need it sorted. Hmm...
> return a
>
Didn't someone already answer that. List addition and sum() both do
what you want.
>>> A = [1,2,3]
>>> B = [4,5,6]
>>> C = [7,8,9]
>>> A+B+C
[1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> sum([A,B,C], [])
[1, 2, 3, 4, 5, 6, 7, 8, 9]
It doesn't get any easier than that.
Gary Herron
> DaveM
> --
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