`next()` Function in Python [ English ]

Languages

• English

1. Introduction

The next() function in Python is a built-in function used to retrieve the next item from an iterator. Iterators are objects that allow sequential access to elements of a collection such as a list, tuple, or string.

When next() is called, it returns the next value from the iterator. If there are no more elements left, Python raises a StopIteration exception.

The next() function is commonly used together with the iter() function, which creates an iterator from an iterable object.

2. Syntax

next(iterator, default)

Parameters

1. iterator An iterator object from which the next element will be returned.

2. default (optional) A value that will be returned if the iterator has no more elements. If this parameter is not provided and the iterator is exhausted, Python raises a StopIteration error.

Return Value

• Returns the next element from the iterator.

3. Basic Example

numbers = [10, 20, 30]

it = iter(numbers)

print(next(it))
print(next(it))
print(next(it))

Output

10
20
30

Explanation

• iter(numbers) creates an iterator from the list.
• Each call to next() retrieves the next element in the sequence.

4. Example Showing StopIteration

numbers = [1, 2]

it = iter(numbers)

print(next(it))
print(next(it))
print(next(it))

Output

1
2
StopIteration

Explanation

• After all elements are returned, calling next() again raises a StopIteration exception.

5. Using next() with a Default Value

numbers = [1, 2]

it = iter(numbers)

print(next(it))
print(next(it))
print(next(it, "No more elements"))

Output

1
2
No more elements

Explanation

• Instead of raising an error, the default value "No more elements" is returned.

6. Example with a String

text = "ABC"

it = iter(text)

print(next(it))
print(next(it))
print(next(it))

Output

A
B
C

Explanation

• Each call to next() returns the next character of the string.

7. Example with a Loop

numbers = [5, 10, 15]

it = iter(numbers)

while True:
    try:
        print(next(it))
    except StopIteration:
        break

Output

5
10
15

Explanation

• The loop continues retrieving elements until the iterator is exhausted.

8. Relationship Between iter() and next()

Example:

numbers = [1, 2, 3]

it = iter(numbers)

print(next(it))

Here:

• numbers → iterable
• it → iterator
• next(it) → returns next element

9. Summary

• next() is a built-in Python function used to retrieve the next element from an iterator.
• It works together with the iter() function.
• When the iterator is exhausted, Python raises a StopIteration exception.
• A default value can be provided to avoid this exception.
• It is commonly used in iterator-based operations and loops.