Palindrome Checking (Python)

# check if a phrase is a palindrome
# tested with Python24      vegaseat     10sep2006

def isPalindrome(phrase):
    """
    take a phrase and convert to all lowercase letters and
    ignore punctuation marks and whitespaces,
    if it matches the reverse spelling then it is a palindrome
    """
    phrase_letters = [c for c in phrase.lower() if c.isalpha()]
    print phrase_letters  # test
    return (phrase_letters == phrase_letters[::-1])


phrase1 = "A man, a plan, a canal, Panama!"  # example with punctuation marks
if isPalindrome(phrase1):
    print '"%s" is a palindrome' % phrase1
else:
    print '"%s" is not a palindrome' % phrase1

print

phrase2 = "Madam in Eden I'm Adam"
if isPalindrome(phrase2):
    print '"%s" is a palindrome' % phrase2
else:
    print '"%s" is not a palindrome' % phrase2