true is semantically irrelevant in this example howeverlater in the book we will see examples where this kind of short-circuit evaluation of boolean expressions is semantically relevant this implementation of ispalindrome is an example of problem-solving principle known as divide-and-conquer (this principle is related to but different from divide-and-conquer algorithmswhich are discussed in the problem-solving principle is to conquer hard problem by breaking it into set of subproblems with the properties that the subproblems are easier to solve than the original problemand solutions of the subproblems can be combined to solve the original problem in this casewe solve the problem by breaking the original problem into simpler version of the same problem (checking whether shorter string is palindrome)plus some simple things we know how to do (comparing single charactersfigure contains some code that can be used to visualize how this works def ispalindrome( )"""assumes is str returns true if is palindromefalse otherwise punctuation marksblanksand capitalization are ignored ""def tochars( ) lower(letters 'for in sif in 'abcdefghijklmnopqrstuvwxyz'letters letters return letters def ispal( )print ispal called with' if len( < print about to return true from base casereturn true elseanswer [ = [- and ispal( [ :- ]print about to return'answer'for' return answer return ispal(tochars( )def testispalindrome()print 'try doggodprint ispalindrome('doggod'print 'try dogoodprint ispalindrome('dogood'figure code to visualize palindrome testing