Python iter() Function

The Python iter() function is used to create iterator object from an iterable object. The next() method can be used to access next element of the iterator.

Syntax

iter(object, sentinel)

Parameters

Example: using iter() function

In the example below, an iterator called MyIter is created from a list called MyList and after that next() method is used to access next element of the iterator. Please note that, a StopIteration exception is raised when the iterator do not have more elements to iterate upon.

MyList = [10, 20, 30, 40, 50]
MyIter = iter(MyList)

print(next(MyIter))
print(next(MyIter))
print(next(MyIter))
print(next(MyIter))
print(next(MyIter))
print(next(MyIter))

The output of the above code will be:

10
20
30
40
50

Traceback (most recent call last):
  File "Main.py", line 9, in <module>
    print(next(MyIter))
StopIteration

Example: using iter() function with sentinel parameter

In the example below, an iterable object called MyIter is created which returns square of natural numbers. The iteration stops when the returned value becomes 81.

class square:
  def __init__(self):
    self.start = 0

  def __iter__(self):
    return self

  def __next__(self):
    self.start += 1
    return self.start**2

  __call__ = __next__

MyIter = iter(square(), 81)  

for i in MyIter:
  print(i)

The output of the above code will be:

1
4
9
16
25
36
49
64