Python - Test String in Character List and vice-versa

Last Updated : 23 Jul, 2025

Given a String, check if it's present in order in the character list and vice versa.

Input : test_str = 'geeks', K = ['g', 'e', 'e', 'k', 'f', 'o', 'r', 'g', 'e', 'e', 'k', 's'] [ String in Character list ]
Output : True
Explanation : geeks is present in list , starting from 7th index till end.

Input : test_str = 'geeksforgeeks', K = ['g', 'e', 'e', 'k', 's'] [Character list in String]
Output : True
Explanation : ['g', 'e', 'e', 'k', 's'] present in string, starting from the beginning of string.

Method #1: Using in operator + join() [ String in character list ]

In this, we convert the character list to a string using join() and apply it in the operator to test for substring presence.

Python3

# Python3 code to demonstrate working of 
# Test String in Character List and vice-versa
# Using in operator and join() [String in list]

# initializing string
test_str = 'geeks'

# printing original string
print("The original string is : " + str(test_str))

# initializing Character list
K = ['g', 'e', 'e', 'k', 'f', 'o', 'r', 'g', 'e', 'e', 'k', 's']

# joining list
joined_list = ''.join(K)

# checking for presence
res = test_str in joined_list

# printing result 
print("Is String present in character list : " + str(res))

Output

The original string is : geeks
Is String present in character list : True

Time Complexity: O(n)
Auxiliary Space: O(n)

Method #2 : Using in operator + join() [ Character List in String ]

In this, the target character list is converted to String and then checked in String using in operator.

Python3

# Python3 code to demonstrate working of 
# Test String in Character List and vice-versa
# Using in operator + join() [ Character List in String ]

# initializing string
test_str = 'geeksforgeeks'

# printing original string
print("The original string is : " + str(test_str))

# initializing Character list
K = ['g', 'e', 'e', 'k', 's']

# joining list
joined_list = ''.join(K)

# checking for presence
res = joined_list in test_str

# printing result 
print("Is character list present in String : " + str(res))

Output

The original string is : geeksforgeeks
Is character list present in String : True

Time Complexity: O(n) -> as join method takes O(n) complexity
Auxiliary Space: O(n)

Method 3 : using the set() function and intersection() method

Step-by-step approach:

Initialize the original string and print it.
Initialize the character list.
Convert the character list to a set using the set() function.
Get the intersection of the character set and the set of the original string using the intersection() method.
Check if the length of the intersection set is equal to the length of the character set.
Print the result.

Python3

# Python3 code to demonstrate working of 
# Test String in Character List and vice-versa
# Using set() and intersection() [ Character List in String ]

# initializing string
test_str = 'geeksforgeeks'

# printing original string
print("The original string is : " + str(test_str))

# initializing Character list
K = ['g', 'e', 'e', 'k', 's']

# converting list to set
char_set = set(K)

# getting intersection of sets
intersect_set = char_set.intersection(set(test_str))

# checking if all characters are present
res = len(intersect_set) == len(char_set)

# printing result 
print("Is character list present in String : " + str(res))

Output

The original string is : geeksforgeeks
Is character list present in String : True

Time complexity: O(n), where n is the length of the original string.
Auxiliary space: O(k), where k is the length of the character list.

manjeet_04

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Python - Test String in Character List and vice-versa

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