Dictionary from list?

[Michael Hudson]

"Ivan A. Vigasin" <vig at ParallelGraphics.COM> writes:

> On Fri, 19 Oct 2001, Michael Hudson wrote:
> 
> > />> def beargh(d):
> > |..     unique = []
> > |..     def ouch(x,y):
> > |..         if x is unique:
> > |..             return y
> > |..         else:
> > |..             d[x] = y
> > |..             return unique
> > |..     return ouch
> > \__
> > ->> d = {}
> > ->> reduce(beargh(d), ['a', 1, 'b', 2])
> > []
> > ->> d
> > {'a': 1, 'b': 2}
> Idea is great! 

You mean that for real?  I think it's foul.  It abuses the
implementation details of reduce to do something that function was
never intended to do.

> It comes from functional programming?

No.  There are side-effects all over the place!

> Your code doesn't work in my Python 2.1 ...
> 
> t1.py:1: SyntaxWarning: local name 'd' in 'beargh' shadows use of 'd' as global in nested scope 'ouch'
>   def beargh(d):
> t1.py:1: SyntaxWarning: local name 'unique' in 'beargh' shadows use of 'unique' as global in nested scope 'ouch'
>   def beargh(d):
> Traceback (most recent call last):
>   File "t1.py", line 12, in ?
>     reduce(beargh(d), ['a', 1, 'b', 2])
>   File "t1.py", line 4, in ouch
>     if x is unique:
> NameError: global name 'unique' is not defined

You needed a "from __future__ import nested_scopes" in there
somewhere.

> I slighly modified your code and got the following:
> 
> class beargh:
>   def __init__(self,d):
>     self.d = d
>   def __call__(self,x,y):
>     if x == []:
>       return y
>     else:
>       self.d[x] = y
>       return []
> 
> d = {}
> reduce( beargh(d), ['a', 1, 'b', 2] )
> print d

Actually, that works almost as well as my code -- you get problems
with input like ['a', 1, [], 2], but you have problems with that
anyway as lists aren't hashable.

Just in case anyone hasn't got the message yet:

THE CODE I POSTED WAS DISGUSTING.  DON'T EMULATE IT.
THE CODE I POSTED WAS DISGUSTING.  DON'T EMULATE IT.
THE CODE I POSTED WAS DISGUSTING.  DON'T EMULATE IT.
THE CODE I POSTED WAS DISGUSTING.  DON'T EMULATE IT.
THE CODE I POSTED WAS DISGUSTING.  DON'T EMULATE IT.
THE CODE I POSTED WAS DISGUSTING.  DON'T EMULATE IT.
THE CODE I POSTED WAS DISGUSTING.  DON'T EMULATE IT.
THE CODE I POSTED WAS DISGUSTING.  DON'T EMULATE IT.
THE CODE I POSTED WAS DISGUSTING.  DON'T EMULATE IT.
THE CODE I POSTED WAS DISGUSTING.  DON'T EMULATE IT.
THE CODE I POSTED WAS DISGUSTING.  DON'T EMULATE IT.
THE CODE I POSTED WAS DISGUSTING.  DON'T EMULATE IT.
THE CODE I POSTED WAS DISGUSTING.  DON'T EMULATE IT.
THE CODE I POSTED WAS DISGUSTING.  DON'T EMULATE IT.
THE CODE I POSTED WAS DISGUSTING.  DON'T EMULATE IT.
THE CODE I POSTED WAS DISGUSTING.  DON'T EMULATE IT.

Cheers,
M.

-- 
  Now this is what I don't get.  Nobody said absolutely anything
  bad about anything.  Yet it is always possible to just pull
  random flames out of ones ass.
         -- http://www.advogato.org/person/vicious/diary.html?start=60