Fredrik Lundh wrote:
> John Reese wrote:
>
> > It seems like it would be clear and mostly backwards compatible if the
> > + operator on any iterables created a new iterable that iterated
> > throught first its left operand and then its right, in the style of
> > itertools.chain.
>
> you do know that "iterable" is an informal interface, right? to what
> class would you add this operation?
>
> </F>
The base object class would be one candidate, similarly to the way
__nonzero__ is defined to use __len__, or __contains__ to use __iter__.
Alternatively, iter() could be a wrapper type (or perhaps mixin)
instead of a function, something like:
from itertools import chain, tee, islice
import __builtin__
_builtin_iter = __builtin__.iter
class iter(object):
def __init__(self, iterable):
self._it = _builtin_iter(iterable)
def __iter__(self):
return self
def next(self):
return self._it.next()
def __getitem__(self, index):
if isinstance(index, int):
try: return islice(self._it, index, index+1).next()
except StopIteration:
raise IndexError('Index %d out of range' % index)
else:
start,stop,step = index.start, index.stop, index.step
if start is None: start = 0
if step is None: step = 1
return islice(self._it, start, stop, step)
def __add__(self, other):
return chain(self._it, other)
def __radd__(self,other):
return chain(other, self._it)
def __mul__(self, num):
return chain(*tee(self._it,num))
__rmul__ = __mul__
__builtin__.iter = iter
if __name__ == '__main__':
def irange(*args):
return iter(xrange(*args))
assert list(irange(5)[:3]) == range(5)[:3]
assert list(irange(5)[3:]) == range(5)[3:]
assert list(irange(5)[1:3]) == range(5)[1:3]
assert list(irange(5)[3:1]) == range(5)[3:1]
assert list(irange(5)[:]) == range(5)[:]
assert irange(5)[3] == range(5)[3]
s = range(5) + range(7,9)
assert list(irange(5) + irange(7,9)) == s
assert list(irange(5) + range(7,9)) == s
assert list(range(5) + irange(7,9)) == s
s = range(5) * 3
assert list(irange(5) * 3) == s
assert list(3 * irange(5)) == s
George
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