How do you find the length of a string in python?

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Python len() function returns the length of the string. 

Python len() Syntax

Syntax: len(string) 

Return: It returns an integer which is the length of the string. 

Python len() Example

len() methods with string in Python.

Python3

string = "Geeksforgeeks"

print(len(string))

Output:

13

Example 1: Len() function with tuples and string

Here we are counting length of the tuples and list.

Python

tup = (1,2,3)

print(len(tup))

l = [1,2,3,4]

print(len(l))

Output: 

3
4

Example 2: Python len() TypeError

Python3

Output:

TypeError: object of type 'bool' has no len()

Example 3: Python len() with dictionaries and sets

Python3

dic = {'a':1, 'b': 2}

print(len(dic))

s = { 1, 2, 3, 4}

print(len(s))

Output:

2
4

Example 4: Python len() with custom objects

Python3

class Public:

    def __init__(self, number):

        self.number = number

    def __len__(self):

        return self.number

obj = Public(12)

print(len(obj))

Output:

12

Time complexity : 

len() function  has time complexity of O(1). in average and amortized case

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Strings in Python are immutable sequences of Unicode code points. Given a string, we need to find its length. Examples:

Input : 'abc'
Output : 3

Input : 'hello world !'
Output : 13

Input : ' h e l   l  o '
Output :14

Methods#1:

• Using the built-in function len. The built-in function len returns the number of items in a container. 

Python3

str = "geeks"

print(len(str))

Method#2:

• Using for loop and in operator. A string can be iterated over, directly in a for loop. Maintaining a count of the number of iterations will result in the length of the string. 

Python3

def findLen(str):

    counter = 0   

    for i in str:

        counter += 1

    return counter

str = "geeks"

print(findLen(str))

Method#3:

• Using while loop and Slicing. We slice a string making it shorter by 1 at each iteration will eventually result in an empty string. This is when while loop stops. Maintaining a count of the number of iterations will result in the length of the string. 

Python3

def findLen(str):

    counter = 0

    while str[counter:]:

        counter += 1

    return counter

str = "geeks"

print(findLen(str))

Method#4:

• Using string methods join and count. The join method of strings takes in an iterable and returns a string which is the concatenation of the strings in the iterable. The separator between the elements is the original string on which the method is called. Using join and counting the joined string in the original string will also result in the length of the string. 

Python3

def findLen(str):

    if not str:

        return 0

    else:

        some_random_str = 'py'

        return ((some_random_str).join(str)).count(some_random_str) + 1

str = "geeks"

print(findLen(str))

Method:5:

• Using reduce method. Reduce method is used to iterate over the string and return a result of collection element provided to the reduce function. We will iterate over the string character by character and count 1 to result each time. 

Python3

import functools

def findLen(string):

    return functools.reduce(lambda x,y: x+1, string, 0)

string = 'geeks'

print(findLen(string))

Output:

5

Method:6:

• Using sum() and list comprehension function. We use list comprehension for iterating over the string and sum function to sum total characters in string 

Python3

def findLen(string):

    return sum( 1 for i in string);

string = 'geeks'

print(findLen(string))

Output:

5