Generators
What is Python Generator?
Python Generators are the most easiest way of creating iterators.
Simply speaking, a generator is a function that returns an object(iterator) that we can iterate over(one value at a time).
How to Create Generators in Python?
Creating generators in python is very simple.
To create a generator you need to replace return statement from normal function with a yield statement.
The difference between yield and return statement is that , return statement stops or terminates a function entirely.
While yield statement parses the fucntion saving all its states and later continues from there on successive calls.
# A simple generator function
def my_gen():
n = 1
print('This is printed first')
# Generator function contains yield statements
yield n
n += 1
print('This is printed second')
yield n
n += 1
print('This is printed at last')
yield n
>>> # It returns an object but does not start execution immediately.
>>> a = my_gen()
>>> # We can iterate through the items using next().
>>> next(a)
This is printed first
1
>>> # Once the function yields, the function is paused and the control is transferred to the caller.
>>> # Local variables and theirs states are remembered between successive calls.
>>> next(a)
This is printed second
2
>>> next(a)
This is printed at last
3
>>> # Finally, when the function terminates, StopIteration is raised automatically on further calls.
>>> next(a)
Traceback (most recent call last):
...
StopIteration
>>> next(a)
Traceback (most recent call last):
...
StopIteration
Generator using Loop
# A simple generator function
def my_gen():
n = 1
print('This is printed first')
# Generator function contains yield statements
yield n
n += 1
print('This is printed second')
yield n
n += 1
print('This is printed at last')
yield n
# Using for loop
for item in my_gen():
print(item)
