[Tutor] Using 'join ' function to create a string

[Dave Kuhlman]

On Fri, Dec 21, 2007 at 09:33:31AM -0700, Eric Brunson wrote:
> lechtlr wrote:
> > Hi there,
> >
> > I would like to know what is the best way to create a string object 
> > from two different lists using 'join' function. For example, I have X 
> > = ['a', 'b', 'c', 'd', 'e'] and Y = [1, 2, 3, 4, 5]. From X and Y, I 
> > want to create a string Z = 'a:1, b:2, c:3, d:4, e:5'.
> 
> How about something like this:
> 
> ", ".join( '%s:%s' % ( x, y ) for x, y in zip( X, Y ) )

Slick.  I believe that the argument you are passing to join() is
the result of a generator expression.  Am I right?

And, I did not know that str.join(seq) could take an iterator as
opposed to a plain sequence.  Thanks for showing us that.

Back to the original poster's problem, you could also try map() and
a lambda:

    ', '.join(map(lambda x,y: '%s:%s' % (x, y, ), X, Y))

Or, maybe unrolling it makes it more readable:

    In [31]: fn = lambda x,y: '%s:%s' % (x, y, )
    In [32]: ', '.join(map(fn, a, b))
    Out[32]: 'aa:11, bb:22, cc:33'

- Dave

-- 
Dave Kuhlman
http://www.rexx.com/~dkuhlman