python generator

1# A generator-function is defined like a normal function, 
2# but whenever it needs to generate a value, 
3# it does so with the yield keyword rather than return. 
4# If the body of a def contains yield, 
5# the function automatically becomes a generator function.
6# Python 3 example
7def grepper_gen():
8  yield "add"
9  yield "grepper"
10  yield "answer"
11grepper = grepper_gen()
12next(grepper)
13> add
14next(grepper)
15> grepper
16next(grepper)
17> answer

1def gen_nums():
2    n = 0
3    while n < 4:
4        yield n
5        n += 1
6

1# Size of generators is a huge advantage compared to list
2import sys
3
4n= 80000
5
6# List
7a=[n**2 for n in range(n)]
8
9# Generator
10# Be aware of the syntax to create generators, lika a list comprehension but with round brakets
11b=(n**2 for n in range(n))
12
13print(f"List: {sys.getsizeof(a)} bits\nGenerator: {sys.getsizeof(b)} bits")

1def count_to_ten_generator():
2  for number in range(10):
3    yield number
4my_generator = count_to_ten_generator()
5first_number = next(my_generator)
6list_or_the_rest = list(my_generator)