def gen(): yield 1 yield 2 yield 3 yield 4 def gen2(): yield -1 print((yield from gen())) yield 10 yield 11 g = gen2() print(next(g)) print(next(g)) g.close() try: print(next(g)) except StopIteration: print("StopIteration") # Now variation of same test, but with leaf generator # swallowing GeneratorExit exception - its upstream gen # generator should still receive one. def gen3(): yield 1 try: yield 2 except GeneratorExit: print("leaf caught GeneratorExit and swallowed it") return yield 3 yield 4 def gen4(): yield -1 try: print((yield from gen3())) except GeneratorExit: print("delegating caught GeneratorExit") raise yield 10 yield 11 g = gen4() print(next(g)) print(next(g)) print(next(g)) g.close() try: print(next(g)) except StopIteration: print("StopIteration") # Yet another variation - leaf generator gets GeneratorExit, # but raises StopIteration instead. This still should close chain properly. def gen5(): yield 1 try: yield 2 except GeneratorExit: print("leaf caught GeneratorExit and raised StopIteration instead") raise StopIteration(123) yield 3 yield 4 def gen6(): yield -1 try: print((yield from gen5())) except GeneratorExit: print("delegating caught GeneratorExit") raise yield 10 yield 11 g = gen6() print(next(g)) print(next(g)) print(next(g)) g.close() try: print(next(g)) except StopIteration: print("StopIteration")