16 lines
268 B
Python
16 lines
268 B
Python
class Bird:
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pass
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class Duck(Bird): # <1>
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def quack(self):
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print('Quack!')
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def alert(birdie): # <2>
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birdie.quack()
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def alert_duck(birdie: Duck) -> None: # <3>
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birdie.quack()
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def alert_bird(birdie: Bird) -> None: # <4>
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birdie.quack()
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