Python next()

The built-in function next() is used to return the next element from an iterator. Typically this function used in a loop. When it reaches the end of the iterator it will throw an error to avoid this situation we can specify the default value.

next(iterator, default) #where iterable can be list, tuple etc
 

next() Parameters:

Takes two parameters. In this the iterator can be string, bytes, tuple, list, or range and collection can be a dictionary, set, or frozen set.

next() Return Value

If it reaches the end of the iterator and the default value is not specified, it will raise a StopIteration exception.

Examples of next() method in Python

random = [5, 9, 'cat']

# converting the list to an iterator
random_iterator = iter(random)
print(random_iterator)

# Output: 5
print(next(random_iterator))

# Output: 9
print(next(random_iterator))

# Output: 'cat'
print(next(random_iterator))

# This will raise Error
# iterator is exhausted
print(next(random_iterator))
 

Output:

5
9
cat
Traceback (most recent call last):
  File "python", line 18, in 
StopIteration

random = [5, 9]

# converting the list to an iterator
random_iterator = iter(random)

# Output: 5
print(next(random_iterator, '-1'))

# Output: 9
print(next(random_iterator, '-1'))

# random_iterator is exhausted
# Output: '-1'
print(next(random_iterator, '-1'))
print(next(random_iterator, '-1'))
print(next(random_iterator, '-1'))
 

Output:

5
9
-1
-1
-1

# Python next() function example  
number = iter([256, 32, 82]) # Creating iterator  
# Calling function  
item = next(number)   
# Displaying result  
print(item)  
# second item  
item = next(number)  
print(item)  
# third item  
item = next(number)  
print(item)  
# fourth item  
item = next(number) # error, no item is present  
print(item)  
 

Output:

Traceback (most recent call last): 
  File "source_file.py", line 14, in 
    item = next(number)
StopIteration 
256
32
82