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The generator method .close() is used to terminate a generator early. Once the .close() method is called the generator is finished just like the end of a for loop. Any further iteration attempts will raise a StopIteration exception.

def generator(): i = 0 while True: yield i i += 1 my_generator = generator() next(my_generator) next(my_generator) my_generator.close() next(my_generator) # raises StopGenerator exception

In the above example, my_generator() holds an an infinite generator object. After a couple next(my_generator) calls, my_generator.close() is called. When we attempt to call next(my_generator) again, a StopIteration exception is raised.

The .close() method works by raising a GeneratorExit exception inside the generator function. The exception is generally ignored but can be handled using try and except.

def generator(): i = 0 while True: try: yield i except GeneratorExit: print("Early exit, BYE!") break i += 1 my_generator = generator() for item in my_generator: print(item) if item == 1: my_generator.close()
0 1 Early exit, BYE!

Putting the yield expression in a try block we can handle the GeneratorExit exception. In this case, we simply print out a message. Because we interrupted the automatic behavior of the .close() method, we must also use a break to exit the loop or else a RuntimeError will occur.

To practice this further, we can attempt to use the .close() method on our student generator.

Instructions

1.

We have a collection of 5,000 students. We only want to retrieve information on the first 100 students. Use the close() method to terminate the generator after 100 students.

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