You must first know what is the Builder
Generator is iterable, but with a different list, you can only read it once. Generator not return a value, so use the yield.
Use generator may save memory.
Keyword yield
yield characteristics:
- yield analogous to return, but the yield is to generate a return object
- The first iteration of a generator function, from the beginning to the yield, the yield value and then returns as a return value of the first iteration, the next time this function is executed, and a subsequent iteration, rather than starting from scratch.
- When the loop end of the last yield, the generator will be considered vacant.