P2.7.7Determine if a string is a palindrome using recursion
Write a function that determines if a string is a palindrome (that is, reads the same backwards as forwards) using recursion.
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The function defined in the code listing below is explained in its comments.
def is_palindrome(s):
""" Return True is s is a palindrome, else return False. """
if len(s) < 2:
return True
# Return False unless the first and last letters of s are the same
# and the substring between them is a palindrome
return s[0] == s[-1] and is_palindrome(s[1:-1])
test_words = ('thatch', 'minim', 'an', 'i', 'redder')
for word in test_words:
print('Is "{:s}" a palindrome:'.format(word), is_palindrome(word))
Output:
Is "thatch" a palindrome: False
Is "minim" a palindrome: True
Is "an" a palindrome: False
Is "i" a palindrome: True
Is "redder" a palindrome: True