Mastering Python

Chapter 6. Generators and Coroutines – Infinity, One Step at a Time

A generator is a specific type of iterator that generates values through a function. While traditional methods build and return a list of items, a generator will simply yield every value separately at the moment when they are requested by the caller. This method has several benefits:

• Generators pause execution completely until the next value is yielded, which makes them completely lazy. If you fetch five items from a generator, only five items will be generated, so no other computation is needed.
• Generators have no need to save values. Whereas a traditional function would require creating a list and storing all results until they are returned, a generator only needs to store a single ...