example.py

import gc
closed = False


def generator(iterable, held=None):
    global closed
    try:
        for chunk in iterable:
            yield chunk
    except GeneratorExit:
        print('generator exit')
    finally:
        print('held: %r' % held)
        print('closing')
        closed = True

h = []
g = generator(range(5), h)
h.append(g)
del h
for i in g:
    print('break: %r' % closed)
    break

print('before del: %r' % closed)
del g
print('after del: %r' % closed)

print('before gc.collect: %r' % closed)
gc.collect()
print('after gc.collect: %r' % closed)