[Python-ideas] Aid reiteration with new class: gfic
tjreedy at udel.edu
Thu Jun 18 23:02:12 CEST 2009
Most functions that take an iterable as parameter iterate just once.
Users of the function can pass any iterable, including iterators.
The function will call iter(imput) and go.
If the user wants to iterate thru a virtual collection defined by an
instance of an iterator class (built-in or user-defined) or generator
function, the user must call the gf/ic with the appropriate arguments
and pass the result.
Some functions iterate thru the input more than once. If the input is
not an iterator, there is no problem: call iter(input) again. If the
input is an iterator, that just returns the now-empty iterator. Bad.
The most general solution is for the caller to pass the result of
list(it) instead of it. If the caller starts with only an iterator, that
is the only solution I know of.
If the caller starts with an non-iterable iterator source -- iterator
class or generator function (which can be regarded as defining a virtual
subclass of iterator class 'generator') -- it might be better to package
that source and required args as an iterable.
class gfic: #untested as yet
def __init__(self, func, *args, **kwds):
self.func = func
self.args = args
self.kwds = kwds
self.__name__ = func.__name__
return self.func(*self.args, **self.kwds)
This is similar, I believe, to functools.partial except that the
wrapping is total rather than partial and the wrapped call is in
__iter__ instead of __call__.
Would this be a sensible addition to functools, say, or is the use case
Terry Jan Reedy
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