yield

yield is used inside a function like a return statement. But yield returns a generator.

Generator is an iterator that generates one item at a time. A large list of value will take up a lot of memory. Generators are useful in this situation as it generates only one value at a time instead of storing all the values in memory. For example,

>>> g = (2**x for x in range(100))

will create a generator g which generates powers of 2 up to the number two raised to the power 99. We can generate the numbers using the next() function as shown below.

>>> next(g)
1
>>> next(g)
2
>>> next(g)
4
>>> next(g)
8
>>> next(g)
16

And so on… This type of generator is returned by the yield statement from a function. Here is an example.

def generator():
    for i in range(6):
        yield i*i

g = generator()
for i in g:
    print(i)

Output

0
1
4
9
16
25

Here, the function generator() returns a generator that generates square of numbers from 0 to 5. This is printed in the for loop.