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Python len() Function

Determine the number of items in Python objects like strings, lists, dictionaries, and more using the built-in len() function with syntax and practical examples.

The len() function returns the number of items in an object, i.e. the length of the object.

Syntax

len(object)

len() Parameters

Python len() function parameters:

Parameter Condition Description
object Required The object for which the length is to be determined (a sequence or a collection)

len() Return Value

Python len() function returns the number of items of an object.

Examples

Example 1: Length of a String using len() function

Get the length of a string:

name = "Tutorial Reference"
print(len(name))  # Output:  18

output

18

Example 2: Length of a List using len() function

Get the length of a list:

langs = ["Python", "JavaScript", "Rust"]
print(len(langs))  # Output:  3

output

3

Example 3: Length of a Dictionary using len() function

Get the length of a dictionary:

student = {"name": "Tom", "age":  25, "grade": "A"}
print(len(student))  # Output:  3

output

3

Example 4: Length of a Tuple using len() function

Get the length of a tuple:

coordinates = (40.689167,-74.044444)
print(len(coordinates))  # Output:  2

output

2

Example 5: Length of a Set using len() function

Get the length of a set:

unique_numbers = {1,  2,  3,  4,  5}
print(len(unique_numbers))  # Output:  5

output

5

Example 6: Length of a bytes using len() function

Get the length of bytes object:

testByte = b'Python'
print('Length of', testByte, 'is', len(testByte)) # Output: 6

testList = [1, 2, 3]
testByte = bytes(testList)
print('Length of', testByte, 'is', len(testByte)) # Output: 3

output

Length of b'Python' is 6
Length of b'\x01\x02\x03' is 3

Example 7: Length of a custom object using len() function

You have to implement the __len__() method:

class Person:
    def __init__(self, height = 180):
      self.height = height
    
    def __len__(self):
      return self.height

person1 = Session()
print(len(person1))

person2 = Person(210)
print(len(person2))

output

180
210
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