Table of Contents
In this tutorial, we will learn about the Python len() function with the help of examples.
The len()
function returns the number of items (length) in an object.
Example
languages = ['Python', 'Java', 'JavaScript'] # compute the length of languages length = len(languages) print(length) # Output: 3
1. len() Syntax
The syntax of len()
is:
len(s)
2. len() Parameters
The len()
function takes a single argument s, which can be
- sequence – string, bytes, tuple, list, range OR,
- collection – dictionary, set, frozen set
3. len() Return Value
len()
function returns the number of items of an object.
Failing to pass an argument or passing an invalid argument will raise a TypeError
exception.
4. Example 1: How len() works with tuples, lists and range?
testList = [] print(testList, 'length is', len(testList)) testList = [1, 2, 3] print(testList, 'length is', len(testList)) testTuple = (1, 2, 3) print(testTuple, 'length is', len(testTuple)) testRange = range(1, 10) print('Length of', testRange, 'is', len(testRange))
Output
[] length is 0 [1, 2, 3] length is 3 (1, 2, 3) length is 3 Length of range(1, 10) is 9
Visit these pages to learn more about:
- Python Lists
- Python Tuples
- Python range() Method
5. Example 2: How len() works with strings and bytes?
testString = '' print('Length of', testString, 'is', len(testString)) testString = 'Python' print('Length of', testString, 'is', len(testString)) # byte object testByte = b'Python' print('Length of', testByte, 'is', len(testByte)) testList = [1, 2, 3] # converting to bytes object testByte = bytes(testList) print('Length of', testByte, 'is', len(testByte))
Output
Length of is 0 Length of Python is 6 Length of b'Python' is 6 Length of b'\x01\x02\x03' is 3
Visit these pages to learn more about:
6. Example 3: How len() works with dictionaries and sets?
testSet = {1, 2, 3} print(testSet, 'length is', len(testSet)) # Empty Set testSet = set() print(testSet, 'length is', len(testSet)) testDict = {1: 'one', 2: 'two'} print(testDict, 'length is', len(testDict)) testDict = {} print(testDict, 'length is', len(testDict)) testSet = {1, 2} # frozenSet frozenTestSet = frozenset(testSet) print(frozenTestSet, 'length is', len(frozenTestSet))
Output
{1, 2, 3} length is 3 set() length is 0 {1: 'one', 2: 'two'} length is 2 {} length is 0 frozenset({1, 2}) length is 2
Visit these pages to learn more about:
- Python Dictionary
- Python Set
- Python frozenset()
Internally, len()
calls the object’s __len__
method. You can think of len()
as:
def len(s): return s.__len__()
So, you can assign custom length to the object (if necessary)
7. Example 4: How len() works for custom objects?
class Session: def __init__(self, number = 0): self.number = number def __len__(self): return self.number # default length is 0 s1 = Session() print(len(s1)) # giving custom length s2 = Session(6) print(len(s2))
Output
0 6
Related posts:
Python Program to Check Armstrong Number
Python String maketrans()
Deep Learning with Python - Francois Cholletf
How to get current date and time in Python?
Python Decorators
How to Get Started With Python?
Python classmethod()
Python reversed()
Python Program to Convert Two Lists Into a Dictionary
Python Program to Print Hello world!
Python filter()
Python Program to Check Prime Number
Python Program to Get the Full Path of the Current Working Directory
Python Program to Split a List Into Evenly Sized Chunks
Python List insert()
Python String join()
Python Strings
Python File I/O Operation
Python String encode()
Python String istitle()
Python delattr()
Python Program to Generate a Random Number
Python property()
Python Program to Check If a String Is a Number (Float)
Python String count()
Python Program to Convert Decimal to Binary Using Recursion
Python Program to Find the Factorial of a Number
Python Program to Check If Two Strings are Anagram
Python Program to Add Two Numbers
Python Inheritance
Python Set intersection_update()
Python Set intersection()