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Nov 2nd, 2009

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palindrome

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how to check if the string is pallindrome or not in python??

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kisan

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Nov 2nd, 2009

Re: palindrome

There is no built in function that I know of to check that.

On thing you might try doing is reversing the string and then comparing each element.

python Syntax (Toggle Plain Text)
inString = 'racecar'
reversestring = ''
for i in range(0,len(inString)-1:
   reversestring.append(inString[i]
inString = 'racecar'
reversestring = ''
for i in range(0,len(inString)-1:
   reversestring.append(inString[i]

Another way to do it would be to compare the first element to the last element in your string and make sure they match the whole time. One thing that is helpful to remember when doing this is that string[-1] will give you the last element of the string, and string[-2] will give you the second to last. So if your string is racecar then inString[0] should equal inString[-1] and inString[1] should equal inString[-2] etc.

mn_kthompson

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Nov 2nd, 2009

Re: palindrome

there are a couple of posts regarding palindromes in the forum, have a look around.... but basically the algorithm is what mn_kthompson suggested

masterofpuppets

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Nov 3rd, 2009

Re: palindrome

Thank you very much!!
It was helpful. But how could we test if the given string is pallindrome or not. I need a syntax that returns true if the string is pallindrome otherwise false.

kisan

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Nov 3rd, 2009

Re: palindrome

just compare the inString with reversestring using the == operator

Last edited by abhi_elementx; Nov 3rd, 2009 at 6:04 am.

abhi_elementx

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Nov 3rd, 2009

Re: palindrome

Quote ...

But how could we test if the given string is pallindrome or not. I need a syntax that returns true if the string is pallindrome otherwise false.

Python Syntax (Toggle Plain Text)
>>> def is_palindrome(s): 
...     return s.lower() == s[::-1].lower()
... 
>>> is_palindrome('test')
False
>>> is_palindrome('racecar')
True
>>> is_palindrome('RACECAR')
True
>>> def is_palindrome(s): 
...     return s.lower() == s[::-1].lower()
... 
>>> is_palindrome('test')
False
>>> is_palindrome('racecar')
True
>>> is_palindrome('RACECAR')
True

snippsat

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Nov 3rd, 2009

Re: palindrome

bravo!!! snipsat.
Dint know something like this exists in Python.

abhi_elementx

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Nov 3rd, 2009

Re: palindrome

or you could do it using a loop:

Python Syntax (Toggle Plain Text)
def isPalindrome( s ):
    s = s.lower()
    for i in range( len ( s ) / 2 ):
        if s[ i ] != s[ -1 -i ]:
            return False
    return True
 
>>> isPalindrome( "RACECAr" )
True
>>> isPalindrome( "test" )
False
>>> isPalindrome( "civiC" )
True
>>> isPalindrome( "ciniC" )
True
>>> isPalindrome( "cinac" )
False
>>>
def isPalindrome( s ):
    s = s.lower()
    for i in range( len ( s ) / 2 ):
        if s[ i ] != s[ -1 -i ]:
            return False
    return True

>>> isPalindrome( "RACECAr" )
True
>>> isPalindrome( "test" )
False
>>> isPalindrome( "civiC" )
True
>>> isPalindrome( "ciniC" )
True
>>> isPalindrome( "cinac" )
False
>>>

Last edited by masterofpuppets; Nov 3rd, 2009 at 8:49 am.

masterofpuppets

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Nov 3rd, 2009

Re: palindrome

Let's hope this is not homework and the OP had a chance to learn something.

In a true palindrome test you also need to remove everything but the case adjusted letters.
"Madam in Eden I'm Adam" is a palindrome.

vegaseat

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DaniWeb's Hypocrite

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Nov 4th, 2009

python more

IT was quite helpful. so in case of palindromes how can we remove the symbols and capital letters using .upper and replace function?? for example
"Madam, in Eden I'm Adam!"

kisan

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