The len() function returns the length (the number of items) of an object.
Example
languages = ['Python', 'Java', 'JavaScript']
length = len(languages)
print(length) # Output: 3
len() Syntax
The syntax of len() is:
len(s)
len() Argument
The len() function takes a single object as argument. It can be:
- Sequence - list, tuple, string, range, etc.
- Collection - set, dictionary etc.
len() Return Value
It returns an integer (the length of the object).
Example 1: Working of len() with Tuples, Lists and Range
x = [1, 2, 3]
print(len(x)) # Output: 3
y = (1, 2, 3)
print(len(y)) # Output: 3
z = range(8, 20, 3)
print(len(z)) # Output: 4
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Example 2: len() with Strings, Dictionaries and Sets
text = 'Python'
print(len(text)) # Output: 6
person = {"name": 'Amanda', "age": 21}
print(len(person)) # Output: 2
animals = {'tiger', 'lion', 'tiger', 'cat'}
print(len(animals)) # Output: 3
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len() with User-defined Objects
The len() function internally calls the object's __len__() method. You can think of len() as:
def len(s):
return s.__len__()
Therefore, we can make len() work for a user-defined object by implementing the ___len___() method.
Example 3: len() with User-defined Object
class Session:
def __init__(self, number = 0):
self.number = number
def __len__(self):
return self.number
# default length is 0
session1 = Session()
print(len(session1)) # Output: 0
session2 = Session(6)
print(len(session2)) # Output: 6