Confusion about iterator types
urner at alumni.princeton.edu
Sun Aug 12 00:30:15 CEST 2001
In types, I find SequenceIterType and FunctionIterType.
When I go:
>>> mylist = [1,2,3,4]
>>> myiter = iter(mylist)
I then get:
But 'iterator' by itself has no corresponding type in types.
If I use the isinstance() method, I can confirm that myiter is a
SequenceIterType, but shouldn't it just tell me that? Shouldn't
type(foo) return a type name that more closely matches its type
in types? Why not have?:
Also, some clarification re the below would be helpful:
>>> def f(n): return n*n
>>> k = iter(f,10)
Traceback (most recent call last):
File "<pyshell#142>", line 1, in ?
TypeError: object is not callable: <callable-iterator object at 00B6D10C>
In IDLE, when I go >>> iter( I'm prompted that the syntax is
iter(collection) -> iterator. Yet the PEP leads me to this other use
of iter(v, w) where v must be callable.
Simply obeying that rule allows me to get as far as defining f above
(callable) and getting some callable-iterator k. I don't know what this
should mean or do in this context, but it's apparently legal -- until I
actually try to call this callable-iterator, and get the error message that
this object isn't callable. Just from a logical consistency point of view,
it seems that any object calling itself a callable-iterator shouldn't turn
around and tell me it ain't callable.
And again, there's no 'callable-iterator' type in types.
I find that my object is a FunctionIterType:
Seems the types name should therefore be CallableIter or the returned
type should be <type 'function-iter'> (corresponding to <type 'sequence-iter'>).
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