# Python – Ways to find length of list

## Python | Ways to find length of list

List being an integral part of Python day-day programming has to be learned by all the python users and having a knowledge of its utility and operations is essential and always a plus. So this article discusses one such utility of finding the no. of elements in a list.

Method 1 : Naive Method

In this method one just runs a loop and increases the counter till the last element of the list to know its count. This is the most basic strategy that can be possibly employed in the absence of other present techniques.

Code #1 : Demonstrating finding length of list using Naive Method

 `# Python code to demonstrate` `# length of list` `# using naive method` ` ` `# Initializing list ` `test_list ``=` `[ ``1``, ``4``, ``5``, ``7``, ``8` `]` ` ` `# Printing test_list` `print` `(``"The list is : "` `+` `str``(test_list))` ` ` `# Finding length of list ` `# using loop` `# Initializing counter` `counter ``=` `0` `for` `i ``in` `test_list:` `     ` `    ``# incrementing counter` `    ``counter ``=` `counter ``+` `1` ` ` `# Printing length of list ` `print` `(``"Length of list using naive method is : "` `+` `str``(counter))`

Output :

```The list is : [1, 4, 5, 7, 8]
Length of list using naive method is : 5
```

Method 2 : Using `len()`

The `len()` method offers the most used and easy way to find length of any list. This is the most conventional technique adopted by all the programmers today.

 `# Python program to demonstrate working` `# of len()` `a ``=` `[]` `a.append(``"Hello"``)` `a.append(``"Geeks"``)` `a.append(``"For"``)` `a.append(``"Geeks"``)` `print``(``"The length of list is: "``, ``len``(a))`

Output:

```The length of list is:  4
```
 `# Python program to demonstrate working` `# of len()` `n ``=` `len``([``10``, ``20``, ``30``])` `print``(``"The length of list is: "``, n)`

Output:

```The length of list is:  3
```

Method 3 : Using `length_hint()`

This technique is lesser known technique of finding list length. This particular method is defined in operator class and it can also tell the no. of elements present in the list.

Code #2 : Demonstrating finding length of list using `len()` and `length_hint()`

 `# Python code to demonstrate` `# length of list` `# using len() and length_hint` `from` `operator ``import` `length_hint` ` ` `# Initializing list ` `test_list ``=` `[ ``1``, ``4``, ``5``, ``7``, ``8` `]` ` ` `# Printing test_list` `print` `(``"The list is : "` `+` `str``(test_list))` ` ` `# Finding length of list ` `# using len()` `list_len ``=` `len``(test_list)` ` ` `# Finding length of list ` `# using length_hint()` `list_len_hint ``=` `length_hint(test_list)` ` ` `# Printing length of list ` `print` `(``"Length of list using len() is : "` `+` `str``(list_len))` `print` `(``"Length of list using length_hint() is : "` `+` `str``(list_len_hint))`

Output :

```The list is : [1, 4, 5, 7, 8]
Length of list using len() is : 5
Length of list using length_hint() is : 5
```

Performance Analysis – Naive vs `len()` vs `length_hint()`

When while choosing amongst alternatives its always necessary to have a valid reason why to chose one over another. This section does a time analysis of how much time it takes to execute all of them to offer a better choice to use.

Code #3 : Performance Analysis

 `# Python code to demonstrate` `# length of list` `# Performance Analysis` `from` `operator ``import` `length_hint` `import` `time` ` ` `# Initializing list ` `test_list ``=` `[ ``1``, ``4``, ``5``, ``7``, ``8` `]` ` ` `# Printing test_list` `print` `(``"The list is : "` `+` `str``(test_list))` ` ` `# Finding length of list ` `# using loop` `# Initializing counter` `start_time_naive ``=` `time.time()` `counter ``=` `0` `for` `i ``in` `test_list:` `     ` `    ``# incrementing counter` `    ``counter ``=` `counter ``+` `1` `end_time_naive ``=` `str``(time.time() ``-` `start_time_naive)` ` ` `# Finding length of list ` `# using len()` `start_time_len ``=` `time.time()` `list_len ``=` `len``(test_list)` `end_time_len ``=` `str``(time.time() ``-` `start_time_len)` ` ` `# Finding length of list ` `# using length_hint()` `start_time_hint ``=` `time.time()` `list_len_hint ``=` `length_hint(test_list)` `end_time_hint ``=` `str``(time.time() ``-` `start_time_hint)` ` ` `# Printing Times of each ` `print` `(``"Time taken using naive method is : "` `+` `end_time_naive)` `print` `(``"Time taken using len() is : "` `+` `end_time_len)` `print` `(``"Time taken using length_hint() is : "` `+` `end_time_hint)`

Output :

```The list is : [1, 4, 5, 7, 8]
Time taken using naive method is : 2.6226043701171875e-06
Time taken using len() is : 1.1920928955078125e-06
Time taken using length_hint() is : 1.430511474609375e-06
```

Conclusion : It can be clearly seen that time taken is naive >> `length_hint()` > len(), hence `len()` is the best choice to use.

Last Updated on November 13, 2021 by admin

## Python list pop() MethodPython list pop() Method

Python list | pop() Python list pop() is an inbuilt function in Python that removes and returns

## SSL Certificate Verification – Python requestsSSL Certificate Verification – Python requests

SSL Certificate Verification – Python requests Requests verifies SSL certificates for HTTPS requests, just like

## Python program to check if a string is palindrome or notPython program to check if a string is palindrome or not

Python program to check if a string is palindrome or not Given a string, write

## Python | Reading contents of PDF using OCR (Optical Character Recognition)Python | Reading contents of PDF using OCR (Optical Character Recognition)

Python | Reading contents of PDF using OCR (Optical Character Recognition) Python is widely used

## What does the if __name__ == “__main__”: do?What does the if __name__ == “__main__”: do?

What does the if __name__ == “__main__”: do? Before executing code, Python interpreter reads source

## Python – Find position of a character in given stringPython – Find position of a character in given string

Python | Find position of a character in given string Given a string and a

## Different ways to clear a list in PythonDifferent ways to clear a list in Python

Different ways to clear a list in Python   There are many ways of clearing

## Pass by reference vs value in PythonPass by reference vs value in Python

Pass by reference vs value in Python Developers jumping into Python programming from other languages