Python | Check if all elements in a list are identical

Checking if all elements in a list are identical means verifying that every item has the same value. It's useful for ensuring data consistency and can be done easily using Python's built-in features.

Examples:

Input: ['a', 'b', 'c']
Output: False

Input: [1, 1, 1, 1]
Output: True

Let's explore different methods to check it.

Using set()

set() function removes duplicate values from a list. So, if all elements in a list are identical, converting it to a set will result in a set with only one element.

li = [1, 1, 1]
res = len(set(li)) == 1
print(res)

True

Explanation: len(set(lst)) == 1 checks if the list has only one unique element.

Using all() with generator expression

all() function along with a generator expression compares each element in a list to the first one. If all comparisons return True, it means all elements in the list are identical.

li = [1, 1, 1]
res = all(x == li[0] for x in li)
print(res)

True

Explanation: checks if all elements in the list li are equal to the first element li[0] using all() with a generator expression.

Using count()

count() method checks if all elements are identical by verifying if the first element appears as many times as the length of the list.

li = [1, 1, 1]
res = li.count(li[0]) == len(li)
print(res)

True

Explanation: li.count(li[0]) == len(li) checks if the first element appears as many times as the total number of elements.

Using list multiplication

It compares the original list with a new list created by repeating the first element len(list) times. If both lists are equal, it means all elements in the original list are identical.

li = [1, 1, 1]
res = li == [li[0]] * len(li)
print(res)

True

Explanation: li == [li[0]] * len(li) checks if the list is equal to a new list made by repeating the first element.

Using map() + lambda + all()

lambda function is applied using map() to compare each element in the list to the first one. The all() function then checks if all comparisons are True, indicating that all elements in the list are identical.

li = [1, 1, 1]
res = all(map(lambda x: x == li[0], li))
print(res)

True

Explanation: all(map(lambda x: x == li[0], li)) checks if every element in the list is equal to the first element using a lambda function, confirming all elements are identical.

Using loop

It uses a for loop to compare each element in the list with the first element. If any element is different, it returns False. If the loop completes without finding a mismatch, it means all elements are identical.

li = [1, 1, 1]
res = True
for x in li:
    if x != li[0]:
        res = False
        break
    
print(res)

True

Explanation: loop compares each element to the first one and if any element is different, it sets res to False, meaning not all elements are identical.

Related Articles:

• set()
• all()
• Generator Expression
• count()
• List in Python
• map()
• lambda function
• Loop in python