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comp.lang.python

Re: dict comprehension

Gary Herron

2/1/2008 6:10:00 AM

Daniel Fetchinson wrote:
> Hi folks,
>
> There is a withdrawn PEP about a new syntax for dict comprehension:
> http://www.python.org/dev/peps... which says:
>
> "Substantially all of its benefits were subsumed by generator
> expressions coupled with the dict() constructor."
>
> What does the author mean here? What's the Preferably One Way (TM) to
> do something analogous to a dict comprehension?
>
See about generator expressions in
http://www.python.org/doc/2.4/whatsnew/....

The dict builtin can build a dictionary from a list (or iterator or
generator creating a list) of tuples. Put them together and get what
you might be tempted to call a dictionary comprehension. For instance:

>>> dict((i,i*i) for i in range(10))
{0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9: 81}

Gary Herron