New (?) suggestion re: 'while x = f(): ...'

[Chris Liechti]

Jeff Epler <jepler at unpythonic.net> wrote in 
news:mailman.1022619227.16027.python-list at python.org:

> Why not abuse the 'for' statement, since it performs an assignment to a
> user-determined name?
> 
> Instead of 
>     x = v
>     if x:
>      ...
> you can write
>     for x in G(v):
>      ...

i don't like that, it doesn't show the programmers intention...
it implies that there is a loop but there isn't one realy.
 
> and instead of
>     while 1:
>      x = f()
>      if not x: break
>      ...
> you can write
>     for x in H(f):
>      ...

this isn't that bad if you have a very good name for H. but are thre realy 
that many usages? most often f is readline but now we can iterate over 
files.
could be interesting in list comprehensions, though.

> Given suitable names for G() and H() (and I haven't thought of any yet)
> does anybody favor this over the "pythonic" syntax?

all the effort just to hide "if not x: break" in H... apart frame making 
the loop slower due to a function call it doesn't increase readabilty for 
me. the other problem is that its limited to a function and it won't be 
realy useful until you have curry'ing at hand too.

> Personally, I think
> I'll stick to doing it in the old-fashioned way, but I wanted to share
> my idea with the world...

Puh, we're lucky <just kidding>. what i realy would like is to have some 
functional stuff in a module and there maybe something like H would have 
its place.
 
chris

> Jeff Epler
> jepler at unpythonic.net
> 
> def G(v):
>     if not v: return ()
>     return (v,)

or: G = lambda v: (v,)*bool(v)

hey, maybe we could do some Python golfing despite some worries about the 
clean syntax <wink>

> def H(f):
>     while 1:
>      v = f()
>      if not v: break
>      yield v

-- 
Chris <cliechti at gmx.net>