Determining if string is palindrome

Question

I wrote two simple functions to determine if a string is a palindrome. I thought they were equivalent, but 2 doesn\'t work. Why is this?

1

Answer 1

In the second one, you need to make a str from the reversed type instance -- it's not hard:

if string == ''.join(reversed(string)):

Answer 2

reversed doesn't create a string but a 'reversed' object:

>>> reversed('radar')
<reversed object at 0x1102f99d0>

As such, the string 'radar' does not compare equal to the object reversed('radar'). To make it work, you need to make sure the reversed object is actually evaluated:

def is_palindrome(string):
    if string == u''.join(reversed(string)):
        return True
    else:
        return False

The u''.join(reversed(string)) inserts u'' in between each of the characters in the string and this leads to the reversed string being turned into a string object.

Answer 3

For strings:

def is_palindrome(s):
    """Return True if a string is a palindrome."""
    return s == s[::-1]

For general iterables (including strings):

def is_palindrome(iterable):
    """Return True if an iterable is a palindrome."""
    if list(iteable) == list(reversed(iterable))

Answer 4

str = input("Enter a string")
print("\n".join(["Inserted string is" + "NOT"*((str[::-1])!=str)+ " a palindrome"]))