On 11/29/2018 8:16 AM, E. Madison Bray wrote:
Okay, let's keep it simple:
m = map(str, [1, 2, 3])
len_of_m = None
if len(m.iters) == 1 and isinstance(m.iters[0], Sized):
len_of_m = len(m.iters[0])
As I have noted before, the existing sized collection __length_hint__
methods (properly) return the remaining items = len(underlying_iterable)
- items_already_produced. This is fairly easy at the C level. The
following seems to work in Python.
class map1:
def __init__(self, func, sized):
"
if isinstance(sized, (list, tuple, range, dict)):
self._iter = iter(sized)
self._gen = (func(x) for x in self._iter)
else:
raise TypeError(f'{size} not one of list, tuple, range, dict')
def __iter__(self):
return self
def __next__(self):
return next(self._gen)
def __length_hint__(self):
return __length_hint__(self._iter)
m = map1(int, [1.0, 2.0, 3.0])
print(m.__length_hint__())
print('first item', next(m))
print(m.__length_hint__())
print('remainer', list(m))
print(m.__length_hint__())
# prints, as expected and desired
3
first item 1
2
remainer [2, 3]
0
A package could include a version of this, possibly compiled, for use
when applicable.
--
Terry Jan Reedy
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