Python Tutorial Was: Guido's regrets: filter and map

[Lulu of the Lotus-Eaters]

"Anders J. Munch" <andersjm at dancontrol.dk> wrote previously:
|> reduce = lambda func, seq, init=None:\
|>          [(l.append(func(l[i],seq[i])),l[-1])
|>                          for l in [[init or seq[0]]]
|>                          for i in range(len(seq))][-1][1]
|
|Needs more "improvement" ;-)
|>>> reduce(operator.add, [1,2,3])
|6
|>>> lulu_reduce(operator.add, [1,2,3])
|7

Yep. I got the stuff with optional 'init' wrong.  Here's a version I am
more confident about:

  reduce_ = lambda func, seq, init=None:\
            [(l.append(func(l[-1],e)),l[-1])
                for l in [init is None and seq[:1] or [init]]
                for e in seq[init is None:]][-1][1]

Bengt Richter proposed a slightly longer version, but it required an
external 'id' variable.  I like mine better, especially now that I got
rid of the 'i' numeric indexing, and just iterate directly over a slice
of 'seq'.

  >>> from sick import reduce_
  >>> from operator import add
  >>> reduce(add, range(5)), reduce_(add, range(5))
  (10, 10)
  >>> reduce(add, range(1,5)), reduce_(add, range(1,5))
  (10, 10)
  >>> reduce(add, range(5), 0), reduce_(add, range(5), 0)
  (10, 10)
  >>> reduce(add, range(1,5), 0), reduce_(add, range(1,5), 0)
  (10, 10)
  >>> reduce(add, range(5), 10), reduce_(add, range(5), 10)
  (20, 20)
  >>> reduce(add, range(1,5), 10), reduce_(add, range(1,5), 10)
  (20, 20)

Yours, Lulu...

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