Combining lists to dictionary

Rob Gaddi rgaddi at technologyhighland.invalid
Tue Nov 11 22:42:30 CET 2014

On Tue, 11 Nov 2014 20:43:01 +0000 (UTC)
Denis McMahon <denismfmcmahon at> wrote:

> Hi
> Given x,y are a lists of keys and value that I wish to combine to a 
> dictionary, such that x[n] is the key for value y[n], which is preferred:
> z = {a:b for (a,b) in zip(x,y)}
> z = {x[n]:y[n] for n in range(min(len(x),len(y)))}
> The zip feels more elegant, but it seems clunky to use the zip method to 
> create a list of tuples just to split them up into key:value pairs. 
> However the zip method handles the inequal length list problem. Granted 
> it would probably be advisable to check that x and y are the same length 
> before starting anyway.
> -- 
> Denis McMahon, denismfmcmahon at

To add to what Gary said, the explicit dict() init knows how to handle
an iterable that emits pairs of data.  So you can simplify further down to:

z = dict(zip(x, y))

If you're running Python2, and really that concerned about the extra
memory used by zip returning a list rather than an iterator, you can
use itertools.izip

Rob Gaddi, Highland Technology --
Email address domain is currently out of order.  See above to fix.

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