How to Check for Palindrome Using Python Logic

How to check for palindrome using Python logic

A pythonic way to determine if a given value is a palindrome:

str(n) == str(n)[::-1]

Explanation:

• We're checking if the string representation of n equals the inverted string representation of n
• The [::-1] slice takes care of inverting the string
• After that, we compare for equality using ==

How to check if a string is a palindrome?

Just reverse the string and compare it against the original

string_to_check = input("Enter a string")

if string_to_check == string_to_check[::-1]:
    print("This is a palindrome")
else:
    print("This is not a palindrome")

Palindrome words check function : python 3

There are a few issues:

• The y variable should start at -1, since it should reference the last character.
• The incremental change to y is not correctly indented, as it should be part of the for loop
• input_string[y] was a good idea, but you need a separate if condition for checking whether that character is a non-blank
• There is a return new_string statement that should not be there, since the final if still needs to be executed

I should also note that this template code is very restrictive and is not promoting a pythonic coding style, but here are the corrections for the above issues:

def is_palindrome(input_string):
    new_string = ""
    reverse_string = ""
    y = -1  # must be -1 not 1
    for letter in input_string:
        if letter != " ":
            new_string     += letter
        if input_string[y] != " ":   # separate condition
            reverse_string += input_string[y]
        y -= 1  # fixed indentation
    
    if new_string.lower() == reverse_string.lower():  # added condition
        return True
    return False

Again, this is not the most elegant solution, nor is it very efficient.

Is this a correct way to get palindrome? I got the result but m not sure

You can check for palindrome without using loops

1. Remove all white spaces in the input string.
2. Convert the string to lower case.
3. Compare the string with its reverse.
4. return the output.

def is_palindrome(input_string):
    string = input_string.replace(" ", "").lower()
    rev_str = string[::-1]

    return string == rev_str

print(is_palindrome("Never Odd or Even"))
print(is_palindrome("abc"))
print(is_palindrome("kayak"))

output:

True
False
True

Function to test if a string is a palindrome

The problem is that the return value of your function is always None, so the assert is_palindrome(...) will fail and raise an AssertionError. Any statement following this (in this case your assert not is_palindrome('house')) will not be executed.

What you need to do is return an appropriate value. For example:

def is_palindrome(s):
    string = s
    if (string==string[::-1]):
        print("The string IS a palindrome")
        return True
    else:
        print("The string is NOT a palindrome")
        return False

Checking if a string is palindrome

It compares the last character with the first and moves inside the string as follows:

hannah
^    ^

check the two letters are equal: (return False if not)
move the index by 1

hannah
 ^  ^

Do the same check

hannah
  ^^

right index = left index at this point

return True in this case

Determining if a number is a palindrome

Try this to check if number is palindrome or not

if str(temp)==str(temp)[::-1]:
    print("Number is palindrome")
else:
    print("Not palindrome")

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