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- """
- Uses a trace function to switch greenlets at unexpected times.
- In the trace function, we switch from the current greenlet to another
- greenlet, which switches
- """
- import greenlet
- g1 = None
- g2 = None
- switch_to_g2 = False
- def tracefunc(*args):
- print('TRACE', *args)
- global switch_to_g2
- if switch_to_g2:
- switch_to_g2 = False
- g2.switch()
- print('\tLEAVE TRACE', *args)
- def g1_run():
- print('In g1_run')
- global switch_to_g2
- switch_to_g2 = True
- from_parent = greenlet.getcurrent().parent.switch()
- print('Return to g1_run')
- print('From parent', from_parent)
- def g2_run():
- #g1.switch()
- greenlet.getcurrent().parent.switch()
- greenlet.settrace(tracefunc)
- g1 = greenlet.greenlet(g1_run)
- g2 = greenlet.greenlet(g2_run)
- # This switch didn't actually finish!
- # And if it did, it would raise TypeError
- # because g1_run() doesn't take any arguments.
- g1.switch(1)
- print('Back in main')
- g1.switch(2)
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