Generators in python

• Implementing the iterator, it is a toughest mechanism.

• Implement the iterator mechanism in easy way or simplified manner we are going to use the concept called Generator.

Generators:

• Generator is a function, which contains one or more yield statements.

• yield statement is also like as a return statement in normal function,that yield statement return's value.

• when ever return statement of a function is executed ,function terminates.

• when ever yield statement of a function is executed,function execution will be paused later we can continue the executes the remaining part of the function.

• when ever we call the generator function it internally returns the generator object.

• generator object is also same like as a iterator object.

• when ever we call the Generator function internally                  _ _iter_ _( ) method and _ _next_ _( ) method are implemented  automatically.

• when ever we call the next( ) function on the generator object ,generator function logic will be executed until yield statements.

• if no more elements in generator object,it raises StopIterationException when ever we call next( ).

def my_gen( ):

    n=1

    print("this is printed first")

    yield n

    n += 1

    print("this is printed second")

    yield n

    n += 1

    print("this is printed last")

    yield n

a=my_gen( )

print(a)

print(next(a))

print(next(a))

print(next(a))

print(next(a))

<generator object my_gen at 0x000000A7EBD0C7D8>

this is printed first

1

this is printed second

2

this is printed last

3

Traceback (most recent call last):

  File "E:/python_practice/examples/generator.py", line 18, in <module>

    print(next(a))

StopIteration

Note:

• Handling the StopIterationException by using For loop .

def my_gen( ):

    n=1

    print("this is printd first")

    yield n

    n += 1

    print("this is printed second")

    yield n

    n += 1

    print("this is printed last")

    yield n

a=my_gen( )

for p in a:

    print(p)

this is printd first

1

this is printed second

2

this is printed last

3

Example: reversing the string

def rev_str(my_str):

    length=len(my_str)

    for i in range(length-1,-1,-1):

        yield my_str[i]

x=rev_str("siva")

for p in x:

    print(p)

a

v

i

s