Scott David Daniels wrote:
> [EMAIL PROTECTED] wrote:
> > Scott David Daniels wrote:
> >> Sorry, "re-iterables". A file re-iterable is:
> >>
> >> class FileReIterable(object): ...
> >> def __iter__(self):
> >> self.file.seek(0)
> >> return iter(self.file)
> >>
> >> This works if-and-only-if it is only in use once at a time.
> >> If you have multiple simultaneous accesses, you need to do
> >> something like:
> >>
> >> class FileReIterable2(object): ...
> >> def __iter__(self):
> >> self.file.seek(0)
> >> for line in self.file:
> >> nextpos = self.file.tell()
> >> yield line
> >> self.file.seek(nextpos)
> >
> > Since I was doing this as a self education excercise. When you say is
> > in use once and only once, you mean I can only use a single instance of
> > the class?
> No. This works:
>
> f1 = FileReIterable("one.file")
> f2 = FileReIterable("another.file")
> ... free uses of ...
>
> This does not "work":
>
> gen = FileReIterable("one.file")
>
> for a in gen:
> for b in gen:
> print a, b
>
> This does "work":
>
> gen = FileReIterable2("one.file")
>
> for a in gen:
> for b in gen:
> print a, b
>
> That is, any instance of FileReIterable must not be used in a
> context where it may be in the midst of iterating a file, gets
> used to produce a result, and then must produce a result from
> the original iteration.
>
> If you think about what must happen to the file read pointer,
> the reason for all of this should become clear.
>
> --Scott David Daniels
> [EMAIL PROTECTED]
Thanks for the explanation, the issue of the file pointer was pretty
clear - it's why I created multiple files. I just misunderstood what
you meant by use only one. What I did miss at first was the fact that
the file object is not re-iterable. Just plain dumb oversite.
Of course in the end I'm actually more concerned with writing my own
iterators or generators. I was to busy thinking my errors were in the
recursion to look at the iterable/reiterable issue. This is a working
version of the die class I started this thread with.
class die(object):
def __init__(self,sides):
self.sides=sides
self.next = 1
def next(self):
if self.next <= self.sides:
current = self.next
self.next +=1
return current
else:
self.next=1
raise StopIteration
def __iter__(self):
return self
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