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

[Erik Max Francis]

Jeremy Fincher wrote:

> The biggest problem with filter, map, and reduce is that they're
> functions, not methods.

But since they can operate on _any_ sequence, this makes the most sense.

> All this discussion about list comprehensions
> versus filter/map ignores one major disadvantage of list
> comprehensions: that they only work with lists.  If filter/map/reduce
> had been *methods* on list objects, then a programmer could implement
> his own container objects (binary trees, subclasses of list, etc.)

But there are several other things that can act as sequence objects,
such as strings, tuples, or user-defined types that don't derive from
list but define a __getitem__ method.  filter, map, and reduce really do
belong in the realm of standalone functions, not methods, because they
can apply to any type that _acts_ as a list, whether or not it is a
list, a builtin sequence, or even something which at first sight doesn't
appear to be a sequence type at all (but acts the part).

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