related lists mean value (golfed)
Peter Otten
__peter__ at web.de
Tue Mar 9 13:02:12 CET 2010
Michael Rudolf wrote:
> OK, I golfed it :D
> Go ahead and kill me ;)
>
> x = [1 ,2, 8, 5, 0, 7]
> y = ['a', 'a', 'b', 'c', 'c', 'c' ]
>
> def f(a,b,v={}):
> try: v[a].append(b)
> except: v[a]=[b]
> def g(a): return sum(v[a])/len(v[a])
> return g
> w = [g(i) for g,i in [(f(i,v),i) for i,v in zip(y,x)]]
>
> print("w is now the list of averages, corresponding with y:\n \
> \n x: %s \n y: %s \n w: %s \n" % (x, y, w))
>
> Output:
> w is now the list of averages, corresponding with y:
>
> x: [1, 2, 8, 5, 0, 7]
> y: ['a', 'a', 'b', 'c', 'c', 'c']
> w: [1.5, 1.5, 8.0, 4.0, 4.0, 4.0]
>>> [sum(a for a,b in zip(x,y) if b==c)/y.count(c)for c in y]
[1.5, 1.5, 8.0, 4.0, 4.0, 4.0]
Peter
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