How to find the length of a string in a list in Python

List in Python

A list in Python is implemented to store the sequence of various types of data. However, there are six data types in Python that are capable of storing the sequences but the most common and reliable type is a list. To learn more about python you can join our Master Python programming course.

Table of Contents Show

List in Python
Technique 1: The len() method to find the length of a list in Python
How to Find the Length of a List in Python
Python | Ways to find length of list
Conclusion:
Find length of a string in python (4 ways)
List in Python

A list is defined as a collection of values or items of different types. The items in the list are separated with a comma (,) and enclosed with the square brackets [].

It is defined as follows:

list1 = ['edureka', 'python', 2019]; list2 = [1, 2, 3, 4, 5 ]; list3 = ["a", "b", "c", "d"];

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Technique 1: The len() method to find the length of a list in Python

Python has got in-built method — len() to find the size of the list i.e. the length of the list.

The len() method accepts an iterable as an argument and it counts and returns the number of elements present in the list.

Syntax:

len(list)

Example:

inp_lst = ['Python','Java','Kotlin','Machine Learning','Keras'] size = len(inp_lst) print(size)

Output:

How to Find the Length of a List in Python

Posted Sep 27, 2020

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2 min read

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Lists are one of the most commonly used data types in Python and are used to store collections of items of the same type.

This article shows how to find the length of a 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

Python3

# 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 the length of any list. This is the most conventional technique adopted by all programmers today.

Python3

# 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

Python3

# 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 a lesser-known technique of finding list length. This particular method is defined in the 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()

Python3

# 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 it’s always necessary to have a valid reason why to choose 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

Python3

# 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:

In the below images, it can be clearly seen that time taken is naive >> length_hint() > len(), but the time taken depends highly on the OS and several of its parameter. In two consecutive runs, you may get contrasting results , in fact sometimes naive takes least time out of three.All the possible 6 permutations are possible.

length_hint() > naive > len(),

naive > len()=length_hint()

naive > length_hint() >len()

len > naive > length_hint() > naive

Article Tags :

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Python list-programs

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Practice Tags :

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Find length of a string in python (4 ways)

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

List in Python

A list in Python is a collection of items/values that can store one or more data types such as string, integer, float, etc. There are six other data types in Python. However, lists are the most commonly used data type in Python.

Lists are created using square brackets [ ], and the elements in the list are separated using commas.

The list is defined as follows –

# List with integers numbers = [1, 2, 3, 4, 5] # List with string fruits = ["apple", "orange", "grapes"] # List with mixed data type mixedlist = [1, "Ninja", 55.22, False,"a"]

Python List length: How to Find Length of List in Python? 2