Which of the following method is used to search of an element in a list?

Introduction

In today’s world, the communication network is expanding at a very fast rate. Businesses are going digital to improve management efficiency. The amount of data generated on the internet is increasing, and as a result, datasets are becoming more complex. It is important to organize, manage, access, and analyze the data carefully and efficiently, a data structure is the most helpful method, and the article focuses on it

Table of Contents Show

Introduction
Python Find in List: How to Find Element in List
Python find in list
sort() method
type() function
append() method
5. Data Structures¶
Check if element exists in list in Python
Method 1: Naive Method
Method 2: Using in
Method 3 : Using set() + in
Method 4 : Using sort() + bisect_left()
Method 5 : Using count()

In computer science, data structures serve as the foundation for abstract data types (ADT), where ADT is the logical form of data types. The physical design of data types is implemented using data structures. various types of data structures are used for different types of applications; some are specialized in specific tasks.

Data structures are referred to as a collection of data values and relationships between them, functions, and operations applicable to the data. so that, users can easily access and modify the data efficiently.

Data structures help us to manage large amounts of data, such as huge databases. Efficient data structures are the fundamental basis for efficient algorithms. Besides efficient storage, data structures are also responsible for the efficient retrieval of data from stored locations. It includes an array, Graph, Searching, Programs, Linked List, Pointer, Stack, Queue, Structure, Sorting, and so forth.

The concepts of searching in a data structure, as well as its methods, are covered in this article.

Python Find in List: How to Find Element in List

Python list is an essential container as it stores elements of all the datatypes as a collection. Knowledge of certain list operations is necessary for day-day programming.

Python find in list

To find an element in the Python list, use one of the following approaches.

Find an element in the list by index in Python.
Python Linear search on the list.

sort() method

The sort() method is a built-in Python method that, by default, sorts the list in ascending order. However, you can modify the order from ascending to descending by specifying the sorting criteria.

Example

Let's say you want to sort the element in prices in ascending order. You would type prices followed by a . (period) followed by the method name, i.e., sort including the parentheses.

prices = [238.11, 237.81, 238.91] prices.sort() print(prices) [237.81, 238.11, 238.91]

type() function

For the type() function, it returns the class type of an object.

Example

Here we will see what type of both fam and fam2 are:

fam = ["liz", 1.73, "emma", 1.68, "mom", 1.71, "dad", 1.89] fam ['liz', 1.73, 'emma', 1.68, 'mom', 1.71, 'dad', 1.89]

Let's see what the type of the object is:

type(fam) list

Now, let's look at fam2.

fam2 = [["liz", 1.73], ["emma", 1.68], ["mom", 1.71], ["dad", 1.89]] fam2 [['liz', 1.73], ['emma', 1.68], ['mom', 1.71], ['dad', 1.89]]

Let's see what the type of the object is:

type(fam2) list

These calls show that both fam and fam2 are in fact lists.

append() method

The append() method will add certain content you enter to the end of the elements you select.

Example

In this example, let’s extend the string by adding “April” to the list with the method append(). Using append() will increase the length of the list by 1.

months = ['January', 'February', 'March'] months.append('April') print(months)

When you run the above code, it produces the following result:

['January', 'February', 'March', 'April']

5. Data Structures¶

This chapter describes some things you’ve learned about already in more detail, and adds some new things as well.

Check if element exists in list in Python

List is an important container in python as if stores elements of all the datatypes as a collection. Knowledge of certain list operations is necessary for day-day programming. This article discusses one of the basic list operations of ways to check the existence of elements in the list.

Method 1: Naive Method

In Naive method, one easily uses a loop that iterates through all the elements to check the existence of the target element. This is the simplest way to check the existence of the element in the list.

Method 2: Using in

Python is the most conventional way to check if an element exists in a list or not. This particular way returns True if an element exists in the list and False if the element does not exist in the list. List need not be sorted to practice this approach of checking.

Code #1: Demonstrating to check the existence of an element in the list using the Naive method and in.

Python3

# Python code to demonstrate
# checking of element existence
# using loops and in
# Initializing list 

test_list = [ 1, 6, 3, 5, 3, 4 ]

print("Checking if 4 exists in list ( using loop ) : ")
# Checking if 4 exists in list 
# using loop

for i in test_list:

if(i == 4) :

print ("Element Exists")

print("Checking if 4 exists in list ( using in ) : ")
# Checking if 4 exists in list 
# using in

if (4 in test_list):

print ("Element Exists")

Output :

Checking if 4 exists in list ( using loop ) : Element Exists Checking if 4 exists in list ( using in ) : Element Exists

Method 3 : Using set() + in

Converting the list into the set and then using in can possibly be more efficient than only using in. But having efficiency for a plus also has certain negatives. One among them is that the order of list is not preserved, and if you opt to take a new list for it, you would require to use extra space. Another drawback is that set disallows duplicity and hence duplicate elements would be removed from the original list.

Method 4 : Using sort() + bisect_left()

The conventional binary search way of testing element existence, hence list has to be sorted first and hence not preserving the element ordering. bisect_left() returns the first occurrence of the element to be found and has worked similarly to lower_bound() in C++ STL.

Note: The bisect function will only state the position of where to insert the element but not the details about if the element is present or not.

Code #2 : Demonstrating to check existence of element in list using set() + in and sort() + bisect_left().

Python3

# Python code to demonstrate
# checking of element existence
# using set() + in
# using sort() + bisect_left()

from bisect import bisect_left ,bisect
# Initializing list 

test_list_set = [ 1, 6, 3, 5, 3, 4 ]

test_list_bisect = [ 1, 6, 3, 5, 3, 4 ]

print("Checking if 4 exists in list ( using set() + in) : ")
# Checking if 4 exists in list 
# using set() + in

test_list_set = set(test_list_set)

if 4 in test_list_set :

print ("Element Exists")

print("Checking if 4 exists in list ( using sort() + bisect_left() ) : ")
# Checking if 4 exists in list 
# using sort() + bisect_left()
test_list_bisect.sort()

if bisect_left(test_list_bisect, 4)!=bisect(test_list_bisect, 4):

print ("Element Exists")

else:

print("Element doesnt exist")

Method 5 : Using count()

We can use the in-built python List method, count(), to check if the passed element exists in List. If the passed element exists in the List, count() method will show the number of times it occurs in the entire list. If it is a non-zero positive number, it means an element exists in the List.

Code #3 : Demonstrating to check the existence of elements in the list using count().

Python3

"""
Python code to demonstrate
checking of element existence
using List count() method
"""
# Initializing list

test_list = [10, 15, 20, 7, 46, 2808]

print("Checking if 15 exists in list")
# number of times element exists in list

exist_count = test_list.count(15)
# checking if it is more then 0

if exist_count > 0:

print("Yes, 15 exists in list")

else:

print("No, 15 does not exists in list")