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.