Lazy-evaluation:
The code is run by once or never ben run.
It is also called call-by-need, since only the code is needed, it would be called.
It reduced the amount of code that is excuted and save the momery.
Strick-evaluation:
The code is run down in a order.
example:
# generator solution
def even_integers_generator(n):
for i in range(n):
if i % 2 == 0:
yield i