The documentation for itertools.product at: https://docs.python.org/3/library/itertools.html#itertools.product
currently says that:

    For example, product(A, B) returns the same as ((x,y) for x in A for y in B)

While this is broadly correct, since product first converts its arguments to tuples, this is not true if A or B are infinite iterables. For example, when A = itertools.count() and B = range(2) then the former runs forever using infinite memory, whereas the latter returns the lazy generator immediately for use.

Would it be clearer / more correct to instead say:

    For example, product(A, B) returns the same as ((x,y) for x in tuple(A) for y in tuple(B))

Thanks for the suggestion, but I will decline.  The existing wording communicates the intended mental relationship between the product() and nested for-loop.  IMO, the proposed change obfuscates that main point.  

The details of how product works are communicated in the pure python equivalent block that follows.  That code clearly shows that each pool is first converted to a tuple.  So, your point about infinite iterators is already covered and doesn't need to be said twice.

We could replace "the same as" with "roughly the same as", but I don't really think that would be an improvement.