#	ref: Zybooks Chapter 7.9 Lab: Palindrome

#  simple is_palindrome.
def is_parlindrome_1(s):
	return s == s[::-1]

#   using an alternative method.
def is_parlindrome_2(s):
	return s == "".join(reversed(s))
	
s1 = "racecar"
s2 = "Racecar"
s3 = "Hello world"
s4 = "A Toyota's a Toyota."
print(f"s1: {s1}")
print(f"s2: {s2}")
print(f"s3: {s3}")
print(f"s4: {s4}")

print(f"is_parlindrome_1(s1): {is_parlindrome_1(s1)}")
print(f"is_parlindrome_1(s2): {is_parlindrome_1(s2)}")
print(f"is_parlindrome_1(s3): {is_parlindrome_1(s3)}")
print(f"is_parlindrome_1(s4): {is_parlindrome_1(s4)}")

print(f"is_parlindrome_2(s1): {is_parlindrome_2(s1)}")
print(f"is_parlindrome_2(s2): {is_parlindrome_2(s2)}")
print(f"is_parlindrome_2(s3): {is_parlindrome_2(s3)}")
print(f"is_parlindrome_2(s4): {is_parlindrome_2(s4)}")

def is_parlindrome_3(s):
    #   case insensitive
    return s.lower() == s[::-1].lower()
    
print(f"is_parlindrome_3(s1): {is_parlindrome_3(s1)}")
print(f"is_parlindrome_3(s2): {is_parlindrome_3(s2)}")
print(f"is_parlindrome_3(s3): {is_parlindrome_3(s3)}")
print(f"is_parlindrome_3(s4): {is_parlindrome_3(s4)}")    

def only_alphabet(s):
    #   return only alphabets in s.
    result = ''
    for char in s:
        if char.isalpha():
            result += char
    return result

def only_alphabet_2(s):
    #   return only alphabets in s.
    return "".join(char for char in s if char.isalpha())

def is_parlindrome_4(s):
    #   case insensitive and remove non alphabetic characters.
    s = only_alphabet(s).lower()
    return s == s[::-1]

print(f"is_parlindrome_4(s1): {is_parlindrome_4(s1)}")
print(f"is_parlindrome_4(s2): {is_parlindrome_4(s2)}")
print(f"is_parlindrome_4(s3): {is_parlindrome_4(s3)}")
print(f"is_parlindrome_4(s4): {is_parlindrome_4(s4)}")