Skip to content
Related Articles

Related Articles

Improve Article
Save Article
Like Article

Python next() method

  • Last Updated : 22 Sep, 2021

Python next() function returns the next item of an iterator. In this article, we will cover next() syntax, next() parameters, next() returns.

Syntax : next(iter, stopdef)

 Attention geek! Strengthen your foundations with the Python Programming Foundation Course and learn the basics.  

To begin with, your interview preparations Enhance your Data Structures concepts with the Python DS Course. And to begin with your Machine Learning Journey, join the Machine Learning - Basic Level Course

Parameters : 



  • iter : The iterator over which iteration is to be performed.
  • stopdef : Default value to be printed if we reach end of iterator.

Returns : Returns next element from the list, if not present prints the default value. If default value is not present, raises the StopIteration error.

Python next() method example

Example 1: Demonstrating the working of next() 

Here we will see the python next() in loop.

Python3




# Python code to demonstrate
# working of next()
 
# initializing list
list1 = [1, 2, 3, 4, 5]
 
# converting list to iterator
list1 = iter(list1)
 
print("The contents of list are : ")
 
# printing using next()
# using default
while (1):
    val = next(list1, 'end')
    if val == 'end':
        print('list end')
        break
    else:
        print(val)

Output:

The contents of list are : 
1
2
3
4
5
list end

Example 2: Get the next item from the iterator

Python3




list1 = [1, 2, 3, 4, 5]
 
# converting list to iterator
list1 = iter(list1)
 
print(list1)
print(next(list1))
print(next(list1))
print(next(list1))

Output:

<list_iterator object at 0x0000021D7C801D88>
1
2
3

Example 3: Passing default value to next()

Python3




list1 = [1, 2, 3, 4, 5]
 
# converting list to iterator
list1 = iter(list1)
 
print(list1)
print(next(list1, -1))
print(next(list1, -1))
print(next(list1, -1))
print(next(list1, -1))
print(next(list1, -1))
print(next(list1, -1))
print(next(list1, -1))

Output:

<list_iterator object at 0x0000021D7AE08908>
1
2
3
4
5
-1
-1

Example 6: Python next() stopiteration

Python3




list1 = [1, 2, 3, 4, 5]
 
# converting list to iterator
list1 = iter(list1)
 
print(list1)
print(next(list1))
print(next(list1))
print(next(list1))
print(next(list1))
print(next(list1))
print(next(list1))

Output:

<list_iterator object at 0x0000021D7ADF55C8>
1
2
3
4
5
---------------------------------------------------------------------------
StopIteration                             Traceback (most recent call last)
<ipython-input-17-02f0e1df3bbe> in <module>
    10 print(next(list1))
    11 print(next(list1))
---> 12 print(next(list1))

StopIteration: 

While calling out of the range of iterator then it rises Stopoteration error, to avoid this error we will use the default value as an argument.

Example 5: Performance Analysis 

Python3




# Python code to demonstrate
# next() vs for loop
import time
 
# initializing list
list1 = [1, 2, 3, 4, 5]
 
# keeping list2
list2 = list1
 
# converting list to iterator
list1 = iter(list1)
 
print("The contents of list are : ")
 
# printing using next()
# using default
start_next = time.time()
while (1):
    val = next(list1, 'end')
    if val == 'end':
        break
    else:
        print(val)
print("Time taken for next() is : " + str(time.time() - start_next))
 
# printing using for loop
start_for = time.time()
for i in list2:
    print(i)
print("Time taken for loop is : " + str(time.time() - start_for))

Output: 

The contents of list are : 
1
2
3
4
5
Time taken for next() is : 5.96046447754e-06
1
2
3
4
5
Time taken for loop is : 1.90734863281e-06

Result: Python next in For loop is a better choice when printing the contents of the list than next().

Applications: next() is the utility function for printing the components of the container of iter type. Its usage is when the size of the container is not known or we need to give a prompt when the list/iterator has exhausted.




My Personal Notes arrow_drop_up
Recommended Articles
Page :