When you use a generator comprehension, you can only use the iterable once. For example.

>>> g = (i for i in xrange(10))
>>> min(g)
0
>>> max(g)
Traceback (most recent call last):File "<stdin>", line 1, in <module>
ValueError: max() arg is an empty sequence

Which is kind of annoying considering that works differently than list comprehensions.

You could do g = lambda (): (i for i in xrange(10)) to make it reusable, but then you have to do g () instead of g (EDIT: The problem with this isn't that g () is too long to type, but that if a function expects an iterable, you can't tell it to do g () instead of g.__iter__()). You could also do

class gObject(object):def __iter__(self): return (i for i in xrange(10))g = gObject()

but that is significantly longer than typing g = (i for i in xrange(10)). Is there a shorter syntax than gObject to accomplish this task?

Notes:

• We may assume that the iterable will not consume elements from other permanent iterables. For example, if I did z = iter(xrange(10)), I would not try to define g = (i for i in z), since that could only work once (without cloning z).
• g will no longer be an iterator. Rather, it will now be an iterable. I am fine with that. Indeed, that is kind of the point.
• It should work for infinite iterables. For example, a list comprehension would not work since it only works in finite cases.
• We may assume that any initialization costs are cheap, so rerunning the code defining g would not be an issue.

I don't fully follow the comments, but itertools.tee can give me multiple iterables:

In [518]: g1,g2,g3 = itertools.tee((i for i in range(10)), 3)
In [519]: min(g1), max(g2)
Out[519]: (0, 9)
In [520]: a = 0
In [521]: while a<10:...:     a += next(g3)      # simulate an infinite sequence...:     
In [522]: a
Out[522]: 10
In [523]: list(g3)
Out[523]: [5, 6, 7, 8, 9]

Or without unpacking:

def foo(g):a=0while a<12:a += next(g)return (a, list(g))In [525]: alist = itertools.tee((i for i in range(10)),3)...: flist = [min, max, foo]...: for f,a in zip(flist, alist):...:     print(f(a))
0
9
(15, [6, 7, 8, 9])

(This is using Py3)