Framework for a beginner

[lkcl luke]

On Thu, Apr 19, 2012 at 1:21 PM, Alek Storm <alek.storm at gmail.com> wrote:
> On Thu, Apr 19, 2012 at 7:12 AM, lkcl luke <luke.leighton at gmail.com> wrote:
>>
>> On Thu, Apr 19, 2012 at 12:20 PM, Alek Storm <alek.storm at 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.