What are generators in Python?

Generators are functions that return an iterable collection of items, one at a time, in a set manner. Generators, in general, are used to create iterators with a different approach. They employ the use of yield keyword rather than return to return a generator object.

Let's try and build a generator for fibonacci numbers -

 

## generate fibonacci numbers upto n

def fib(n):

p, q = 0, 1

while(p < n):

yield p

p, q = q, p + q

x = fib(10) # create generator object

 

## iterating using __next__(), for Python2, use next()

x.__next__() # output => 0

x.__next__() # output => 1

x.__next__() # output => 1

x.__next__() # output => 2

x.__next__() # output => 3

x.__next__() # output => 5

x.__next__() # output => 8

x.__next__() # error

 

## iterating using loop

for i in fib(10):

print(i) # output => 0 1 1 2 3 5 8