Python Program to Remove Palindromic Elements from a List

When it is required to remove palindromic elements from a list, list comprehension and the 'not' operator are used. A palindromic number reads the same forwards and backwards, like 121 or 9.

Example

Below is a demonstration of removing palindromic elements from a list ?

my_list = [56, 78, 12, 32, 4, 8, 9, 100, 11]

print("The list is:")
print(my_list)

my_result = [elem for elem in my_list if int(str(elem)[::-1]) not in my_list]

print("The result is:")
print(my_result)

Output

The list is:
[56, 78, 12, 32, 4, 8, 9, 100, 11]
The result is:
[56, 78, 12, 32, 100]

How It Works

The algorithm works by checking if the reverse of each element exists in the original list. Here's the breakdown ?

• str(elem) converts the number to a string

• [::-1] reverses the string

• int(str(elem)[::-1]) converts the reversed string back to an integer

• not in my_list checks if the reversed number is NOT present in the original list

Alternative Method Using a Helper Function

For better readability, we can create a separate function to check if a number is palindromic ?

def is_palindrome(num):
    return str(num) == str(num)[::-1]

my_list = [56, 78, 121, 32, 4, 8, 9, 100, 11]

print("The list is:")
print(my_list)

my_result = [elem for elem in my_list if not is_palindrome(elem)]

print("The result is:")
print(my_result)

The list is:
[56, 78, 121, 32, 4, 8, 9, 100, 11]
The result is:
[56, 78, 32, 100]

Conclusion

Use list comprehension with string reversal to remove palindromic elements from a list. The helper function approach provides better code readability and reusability.