understand how s and s11 shorten one character and then grow one character at a time because there is no loop.

def toChars(s):
    import string
    #s = string.lower(s)
    s = s.lower()
    ans = ''
    for c in s:
        #if c in string.lowercase:
        if c in s:
            ans = ans + c
    return ans

def isPal(s):
    if len(s) <= 1:
        return True
    else:
        s11=s[1:-1]
        equation=(s[0] == s[-1])
        returnequation=equation
        returnispal=isPal(s[1:-1])
        returnboth=returnequation and returnispal
        return returnboth

def isPalindrome(s):
    """Returns True if s is a palindrome and False otherwise"""
    mychars=toChars(s)
    returnispal=isPal(mychars)
    return returnispal

print (isPalindrome('Guttag'))
print (isPalindrome('Guttug'))
print (isPalindrome('Able was I ere I saw Elba'))
print (isPalindrome('Are we not drawn onward, we few, drawn onward to new era?'))

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I created variables so I can see changes in a debugger ide

in def is Palindrome(s)
I do not understand how s and s11 shorten one character and then grow one character at a time because there is no loop.