Rant (was Re: x*x if x>10

DaveM asma61 at dsl.pipex.com
Sun Jul 27 18:18:22 CEST 2008


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

DaveM



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