string is palindrome or not with python - UnboundLocalError-CodePudding

I create a code to test if the string is palindrome or not. The test pass exept when I give the function one character. at this time I got this error:

UnboundLocalError: local variable 'is_palindrome' referenced before assignment

"""
Given a string str, return true if the str can be palindrome and false if not.

Input: str = "aba"
Output: true


Input: str = "abc"
Output: false
"""

def validPalindrome(str: str) -> bool:
  for i in range(len(str)//2):
    is_palindrome = False
    if str[i] == str[-i-1]:
      is_palindrome = True
  if is_palindrome:
    return True
  else:
    return False


print(validPalindrome('aba'))
print(validPalindrome('abc'))
print(validPalindrome('a'))

CodePudding user response：

When you use if is_palindrome in line 6 of your function, it should have been defined before. if your input is a single character, your input length is 1, and thus 1//2 = 0. program never enters the loop. and thus is_palindrome is never defined. I think changing the program to this would help.

def validPalindrome(str: str) -> bool:
  is_palindrome = True
  for i in range(len(str)//2):
    if str[i] != str[-i-1]:
      is_palindrome = False
      break
  return is_palindrome

CodePudding user response：

You should set the is_palindrome variable in the right scope:

def validPalindrome(str: str) -> bool:
  is_palindrome = False
  ...