Python Generators and Iterators
Iterators
An iterator is an object that contains a countable number of values. In Python, an iterator is an object which implements the iterator protocol, which consists of the methods __iter__() and __next__().
Iterating Through an Iterator
mytuple = ("apple", "banana", "cherry")
myit = iter(mytuple)
print(next(myit))
print(next(myit))
print(next(myit))Generators
Generators are a simple way of creating iterators. A generator is a function that returns an object (iterator) which we can iterate over (one value at a time).
Creating a Generator
It is fairly simple to create a generator in Python. It is as easy as defining a normal function, but with a yield statement instead of a return statement.
def my_generator():
n = 1
print('This is printed first')
yield n
n += 1
print('This is printed second')
yield n
n += 1
print('This is printed at last')
yield n
# Using the generator
for item in my_generator():
print(item)Generator Expressions
Simple generators can be easily created on the fly using generator expressions. The syntax for generator expression is similar to that of a list comprehension in Python, but the square brackets are replaced with round parentheses.
my_list = [1, 3, 6, 10]
generator = (x**2 for x in my_list)
print(next(generator)) # Output: 1
print(next(generator)) # Output: 9