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 Find the Square Root
Python Deeper Insights into Machine Learning - Sebastian Raschka & David Julian & John Hearty
Python Program to Find LCM
Python List append()
Python List reverse()
Python Variables, Constants and Literals
Python Set issubset()
Python Program to Check if a Number is Odd or Even
Python @property decorator
Python Exception Handling Using try, except and finally statement
Python repr()
Python List index()
Python Program to Check If a String Is a Number (Float)
Python Object Oriented Programming
Python timestamp to datetime and vice-versa
Python Program to Get a Substring of a String
Python sorted()
Python Modules
Python slice()
Introduction to Machine Learning with Python - Andreas C.Muller & Sarah Guido
Python Program to Convert Kilometers to Miles
Python pow()
Python Set union()
Python List insert()
Python Program to Remove Punctuations From a String
Python String islower()
Python float()
Python String join()
Python Get Current time
Python property()
Python Machine Learning Cookbook - Practical solutions from preprocessing to Deep Learning - Chris A...
Python String startswith()