g = [(yield i) for i in range(3)]Syntactically this looks like a list comprehension, and g should be a list, right? But actually it is a generator. This code is equivalent to the following code:
def _make_list(it):
result = []
for i in it:
result.append(yield i)
return result
g = _make_list(iter(range(3)))
Due to "yield" in the expression _make_list() is not a function
returning a list, but a generator function returning a generator.
This change in semantic looks unintentional to me. It looks like leaking an implementation detail. If a list comprehension would be implemented not via creating and calling an intermediate function, but via an inlined loop (like in Python 2) this would be a syntax error if used outside of a function or would make an outer function a generator function.
__result = []
__i = None
try:
for __i in range(3):
__result.append(yield __i)
g = __result
finally:
del __result, __i
I don't see how the current behavior can be useful.
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