[Python] Copy a generator

Let's say I have a generator like so

def gen():
a = yield "Hello World"
a_ = a + 1 #Imagine that on my computer "+ 1" is an expensive operation
print "a_ = ", a_
b = yield a_
print "b =", b
print "a_ =", a_
yield b


Now let's say I do

>>> g = gen()
>>> g.next()
>>> g.send(42)
a_ = 43
43


Now we have calculated a_. Now I would like to clone my generator like so.

>>> newG = clonify(g)
>>> newG.send(7)
b = 7
a_ = 43
7


but my original g still works.

>>> g.send(11)
b = 11
a_ = 43
11


Specifically, clonify takes the state of a generator, and copies it. I could just reset my generator to be like the old one, but that would require calculating a_. Note also that I would not want to modify the generator extensively. Ideally, I could just take a generator object from a library and clonify it.

Note: itertools.tee won't work, because it does not handle sends.

Note: I only care about generators created by placing yield statements in a function.

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