Python iter() method
Last Updated :
11 Dec, 2024
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Python iter() method is a built-in method that allows to create an iterator from an iterable. An iterator is an object that enables us to traverse through a collection of items one element at a time. Let’s start by understanding how iter() works with a simple example.
a = [10, 20, 30, 40]
# Convert the list into an iterator
iterator = iter(a)
# Access elements using next()
print(next(iterator))
print(next(iterator))
Output
10 20
Table of Content
Syntax of
iter()methoditerator = iter(iterable)
Parameters
iterable: Any object capable of returning its elements one at a time. Examples include lists, tuples, dictionaries, and strings.Return Type
- Returns an iterator object that can be used with the
next()function or aforloop to access the elements sequentially.
Examples of iter() Method
Using iter() with String
# Convert string to iterator
s = "Python"
iterator = iter(s)
print(next(iterator))
print(next(iterator))
Output
P y
Using iter() with Dictionary
d = {'a': 1, 'b': 2, 'c': 3}
iterator = iter(d)
for key in iterator:
print(key)
Output
a b c
Using iter() with Callable and Sentinel
# Generate numbers until sentinel value is encountered
import random
iterator = iter(lambda: random.randint(1, 5), 3)
for num in iterator:
print(num)
Output
5 5
Frequently Asked Questions on iter() Method
Q1: What happens if we call next() on an iterator with no elements left?
Python raises a
StopIterationexception, indicating the end of the iterator.
Q2: Can we iterate over an iterator more than once?
No, iterators are exhausted after one full iteration. We must recreate the iterator to iterate again.
Q3: How is iter() different from a loop?
A loop implicitly handles the iteration process while
iter()gives us manual control over iteration, element by element.
Q4: Can custom classes use iter()?
Yes, custom classes implementing the
__iter__()and__next__()methods can work withiter().
