Find the Length of a String Without Using len Function in Python

In this program, we are given a string and we have to find out the length of a string without using the len() function in Python. In this article, we will see how we can find the length of a string without using len() function in Python.

Example :

Input:  'abc'
Output : 3
Explanation: Length of 'abc' is 3

Python Program to Calculate the Length of a String Without Using len() Function

Below, are the methods of counting Length Of a String Without Using Length in Python:

• Using For Loop
• Using While Loop
• Using join() Method
• Using reduce() Method

Find the Length of a String Without len() Function Using For Loop

In this example , below Python code defines a function findLen to calculate the length of a string using a for loop and the in operator. It iterates through each character in the string, incrementing a counter for each character. Finally, the function returns the total count.

Python3

# Returns length of string
def findLen(str):
    counter = 0
    for i in str:
        counter += 1
    return counter


str = "geeksforgeeks"
print(findLen(str))

Output

13

Find the Length of a String Without len() FunctionUsing While Loop

In this example, below Python code defines a function `findLen` to calculate the length of a string using a while loop and slicing. It increments a counter while there are characters remaining in the sliced string. Finally, the function returns the total count.

Python3

# Returns length of string
def findLen(str):
    counter = 0
    while str[counter:]:
        counter += 1
    return counter


str = "geeksforgeeks"
print(findLen(str))

Output

13

Find the Length of a String Without len() FunctionUsing join() Method

In this example, below Python code defines a function `findLen` to calculate the length of a string using the `join` method and `count` method. It joins the characters of the string with a random string (‘py’ in this case) and counts the occurrences of that random string plus 1 to determine the length.

Python3

# Returns length of string
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))

Output

5

Find the Length of a String Without len() FunctionUsing reduce() Method

In this example, below Python code demonstrates finding the length of a string without using the built-in `len()` function. Instead, it utilizes the `reduce` method from the `functools` module. The lambda function increments the accumulator `x` for each character `y` in the string.

Python3

import functools

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

# Driver Code
string = 'geeksforgeeks'
print(findLen(string))

Output

13