How to concatenate list members

[Roman Suzi]

On Thu, 30 May 2002, Eric Brunel wrote:

What is wrong with:

sep.join(alist)

?

(or, for older Pythons:

import string
string.join(alist, sep)

> Ruediger Maehl wrote:
> > I would like to concatenate all members of a list of strings.
> > How can I do that?
> > I know, I can use a for loop over all elements and concatenate
> > them to one string. But is there another more efficient solution?
> > # ===========================================
> > def concat1(alist, sep=" "):
> >     res = ""
> >     for e in alist:
> >         res += str(e)
> >         res += sep
> > 
> >     return res[:-1]
> > 
> > a = ["200100002", "200100003", "200100004"]  # many many more to come ...
> > 
> > b = concat1(a, "_")
> > 
> > print b
> > 
> > # and b then looks like this:
> > # "200100002_200100003_200100004"
> 
> Try this:
> 
> def concat1(alist, sep=" "):
>   if not alist: return ''
>   return reduce(lambda x,y,sep=sep: x + sep + y, alist)
> 
> The "if" is necessary because as it's written, the reduce won't work on 
> empty lists.
> 
> If you like one-liners, you can also do this:
> 
> b = (a and reduce(lambda x,y: x + "_" + y, a)) or ''
> 
> HTH
> 

Sincerely yours, Roman A.Suzi
-- 
 - Petrozavodsk - Karelia - Russia - mailto:rnd at onego.ru -