Python Generators

Python Generators

Intro to Generators

A generator function in Python is defined like a normal function, but whenever it needs to generate a value, it does so with the yield keyword rather than return. If the body of a def contains yield, the function automatically becomes a Python generator function.

def generatordemo():
    yield 1
    yield 2
    yield 3

for value in generatordemo():
    print(value)

base) pradeep:~$/usr/local/bin/python3 /Users/pradeep/LearnPython/generator.py
1
2
3
(base) pradeep:~$

Generators to save memory

import sys
mylist = [i for i in range(100000)]
print(sum(mylist))
print(sys.getsizeof(mylist), "bytes")
print(type(mylist))
mygen = (i for i in range(100000))
print(sum(mygen))
print(sys.getsizeof(mygen), "bytes")
print(type(mygen))

As seen in the output, instead of usings Lists, if we use generators, we can save a lot of space.

base) pradeep:~$/usr/local/bin/python3 /Users/pradeep/LearnPython/sizeof.py
4999950000
800984 bytes
<class 'list'>
4999950000
200 bytes
<class 'generator'>
(base) pradeep:~$

sys.getsizeof() will help us find the amount of memory.