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Python program to check if an element is present in list

belongs to collection: Python List Programs

mahmoud2506
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2022-05-22
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Check if an element is present in the list

We will take a list as input from the user and then ask the user to enter the element's value to be searched. Then we will return YES/NO based on whether the element is present in the list or not.

Example:

Input:
[4, 2, 9, 5, 1, 0, 7] element -> 5

Output:
Present

Python provides us multiple ways to perform the tasks. And to check for an element's presence also, we can use multiple ways in which the present can be check.

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mahmoud2506
2022-05-22
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Method 1: Searching technique

To check whether an element is present in a list or not. We can simply use any searching technique and find the element in the list.

Here, we will discept linear search.

  • loop through the list
    • if : list[i] == element
    • found = true
    • break
  • if : found == true
    • print "found"
  • else : print "not found"

Program to check if an element is present in the list

# Python program to check if an 
# element exists in list 

# Getting list from user
myList = []
length = int(input("Enter number of elements: "))
for i in range(0, length):
    value = int(input())
    myList.append(value)
ele = int(input("Enter element to be searched in the list: "))

# checking for the presence of element in list
found = False
for i in myList:
    if(i == ele) :
        found = True
        break
if(found):
    print("Element found")
else :
    print("Element not found!")

Output:

Enter number of elements: 5
2
6
8
4
1
Enter element to be searched in the list: 4
Element found

Method 2: Using in operator

Python programming language provides us an operator "in" to check whether an element is present in a list.

Syntax:

Returns boolean values based on the presence of element in the list.

Algorithm:

  • Get the list and seach_element from the user.
  • Check if the element is present in list using in
    • if seach_element in list
      • Print "element found"

Program to check if an element is present in a list using in operator

# Python program to check if an element 
# exists in list 

# Getting list from user
myList = []
length = int(input("Enter number of elements: "))
for i in range(0, length):
    value = int(input())
    myList.append(value)

ele = int(input("Enter element to be searched in the list: "))

# checking for the presence of element in list

if(ele in myList):
    print("Element found")
else :
    print("Element not found!")

Output:

Enter number of elements: 5
10
20
30
40
50
Enter element to be searched in the list: 30
Element found

Method 3: Using bisect_left() method on sorted list

The list needs to be sorted in order to apply this method.

The bisect_left() method find's and returns the first occurrence of the given element in a sorted array.

Syntax:

For sorting list
    list_name.sort()
bisect_left method : 
		bisect_left(list, element)

Returns a boolean value based on whether the element is present in the list or not.

Program to check if an element is present in list

# Python program to check if an element 
# exists in list 

import bisect

# Getting list from user
myList = []
length = int(input("Enter number of elements: "))
for i in range(0, length):
    value = int(input())
    myList.append(value)

ele = int(input("Enter element to be searched in the list: "))

# checking for the presence of element in list
myList.sort()
if(bisect.bisect_left(myList, ele) ):
    print("Element found")
else :
    print("Element not found!")

Output:

Enter number of elements: 5
10
12
15
20
25
Enter element to be searched in the list: 25
Element found

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