How to write this as a list comprehension?

[Rustom Mody]

On Saturday, January 18, 2014 4:49:55 AM UTC+5:30, Piet van Oostrum wrote:
> Hi,

> I am looking for an elegant way to write the following code as a list
> comprehension:

> labels = []
> for then, name in mylist:
>     _, mn, dy, _, _, _, wd, _, _ = localtime(then)
>     labels.append(somefunc(mn, day, wd, name))

> So mylist is a list of tuples, the first member of the tuple is a time
> (as epoch offset) and I neeed to apply a function on some fields of the
> localtime of it.

> I could define a auxiliary function like:

> def auxfunc(then, name):
>     _, mn, dy, _, _, _, wd, _, _ = localtime(then)
>     return somefunc(mn, day, wd, name)

> and then use 
> [auxfunc(then, name) for then, name in mylist]

> or even
> [auxfunc(*tup) for tup in mylist]

> But defining the auxfunc takes away the elegance of a list comprehension. I would like to integrate the unpacking of localtime() and calling somefunc within the list comprehension, but I don't see a simple way to do that.

> somefunc(mn, day, wd, name) for _, mn, dy, _, _, _, wd, _, _ in [localtime(then)] 
> (i.e. using a list comprehension on a one element list to do the variable shuffling) 
> works but I don't find that very elegant.

> labels = [somefunc(mn, day, wd, name) 
>             for then, name in mylist
>             for _, mn, dy, _, _, _, wd, _, _ in [localtime(then)]]

> Python misses a 'where' or 'let'-like construction as in Haskell.

+1
Yes Ive often been bitten by the lack of a 'comprehension-let'

Something like this is possible??


[somefunc(mn,day,wd,name) for (_, mn,dy,_,_,_,wd,_,_), name) in [localtime(then), name for then, name in mylist]]

Some debugging of the structure will be necessary (if at all possible)
I dont have your functions so cant do it