The Python Apprentice

Generators are iterators

The alphabet g is a generator object. Generators are, in fact, Python iterators, so we can use the iterator protocol to retrieve – or yield – successive values from the series:

>>> next(g)1>>> next(g)2>>> next(g)3

Take note of what happens now that we've yielded the last value from our generator. Subsequent calls to next() raise a StopIteration exception, just like any other Python iterator:

>>> next(g)Traceback (most recent call last):  File "<stdin>", line 1, in <module>StopIteration

Because generators are iterators, and because iterators must also be iterable, they can be used in all the usual Python constructs which expect iterable objects, such as for-loops:

>>> for v in gen123():...     print(v)...123

Be aware that ...