Generators

Generators are based on the concept of iteration, as we said before, and they allow coding patterns that combine elegance with efficiency.

Generators are of two types:

• Generator functions: These are similar to regular functions, but instead of returning results through return statements, they use yield, which allows them to suspend and resume their state between each call.
• Generator expressions: These are similar to the list comprehensions we have seen in this chapter, but instead of returning a list, they return an object that produces results one by one.

Generator functions

Generator functions behave like regular functions in all respects, except for one difference: instead of collecting results and returning them at once, they are automatically turned into iterators that yield results one at a time.

Suppose we asked you to count from 1 to 1,000,000. You start, and at some point, we ask you to stop. After some time, we ask you to...