On Thu, Apr 19, 2012 at 1:21 PM, Alek Storm <alek.st...@gmail.com> wrote:
> On Thu, Apr 19, 2012 at 7:12 AM, lkcl luke <luke.leigh...@gmail.com> wrote:
>>
>> On Thu, Apr 19, 2012 at 12:20 PM, Alek Storm <alek.st...@gmail.com> wrote:
>> > Why not use list comprehension syntax?
>>
>> because it's less characters to type, and thus less characters to
>> read. i find that syntax incredibly klunky. left to right you're
>> reading, "you declare something to be the case... and then oh whoops
>> actually it's not really the case because it's modified by a list
>> thing" - it breaks reading expectations.
>>
>> that's what i meant about beauty and elegance. the "bang per buck"
>> ratio in python, results obtained for the number of characters used,
>> is higher, and that's something that i personally find to be a
>> priority over speed.
>
>
> Did I miss something? `[a+1 for a in some_list]` is shorter than both
> `map(lambda a: a+1, some_list)` and `some_list.map(lambda a: a+1)`.
:)
yes you missed something. :)
a) if you use that lambda a:a+1 a lot, you make it an actual
function, don't you? even for clarity you'd still probably use a
function not a lambda. i use map quite a lot, filter and reduce not
so much. a more real-world example was one that i actually gave
initially: map(str, l). or, the syntax i really prefer which doesn't
exist: l.map(str). or, one that i also use in web applications or
their back-ends: map(int, l). if you have a comma-separated set of
variables in a single string, like this: "5, 20, 3", i tend to use
this:
from string import strip
l = map(int, map(strip, l.split(",")))
ok to make it clearer i sometimes do that on 3 separate lines.
i'd _love_ it to be this:
l = l.split(",").map(strip).map(int)
or even better would be this:
l = l.split(",").map(strip, int)
b) read the text from left to right, in plain english:
* map(str, l): you're going to map i.e. apply a string function to a
list's members.
(now you see why i keep getting confused with "map", because the
natural language version of this is "map a list's members to a string"
- the other way round)
* a+1 for a in l: take an expression which is a mathematical
operation and therefore has the expectation that its arguments are
mathematical in nature. then oh damn it wait a minute, actually
there's more going on here: for every variable in a list, use the
variables in the expression to make a new list...
i'm belabouring the point (not entirely intentionally) but you see how
clumsy that is? it's probably just as complex in the actual
lexer/grammar file in the http://python.org source code itself, as it
is to think about in real life and to psychologically parse in
english. you actually have to think *backwards*!
is that clearer, or have i added mud? :)
l.
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