=0` if omitted). A real-world scenario is implementing a custom immutable sequence (like a read-only log) where you must support slicing without allowing modification, so `__setitem__` is intentionally omitted.","keyConcepts":[],"faqs":[],"eliminationLogic":null,"exhibitText":null,"exhibitUrl":null,"hasExhibit":false,"isExhibitQuestion":false,"questionPairs":null,"hasMatchingPairs":false,"isMatchingQuestion":false,"relatedQuestions":[],"breadcrumbItems":null,"nextQuestionUrl":null,"previousQuestionUrl":null,"domainPracticeUrl":null,"certificationUrl":null,"domainUrl":null,"hasAnswerOptions":true,"updatedAt":"2026-06-30T18:05:05.659+00:00","questionType":"multiple_choice"},{"id":"062eafd7-62f1-4666-8a38-0ee6a343c2e8","slug":"refer-to-the-exhibit-what-is-the-output-note-actual-mro-teiqj","certificationSlug":"python-pcap","examCode":"PCAP","examName":"Certified Associate Python Programmer PCAP","questionText":"Refer to the exhibit. What is the output? (Note: actual MRO may vary; choose the one that matches Python 3 C3 linearization.)","difficulty":"hard","domain":"Object-Oriented Programming","domainSlug":"oop","topic":"","questionNumber":0,"totalQuestions":0,"options":[{"key":"A","isCorrect":false,"text":"(, , , )","explanation":"This tuple omits object, the universal root of Python's new-style class hierarchy. C3 linearization always appends object as the final class, because every class ultimately inherits from it even when no explicit base is written. Removing object would leave the MRO without the required common-superclass fallback for special methods like __repr__ and __eq__, so this cannot be what D.__mro__ actually returns.","masteryContext":""},{"key":"B","isCorrect":true,"text":"(, , , , )","explanation":"This is the exact tuple produced by C3 linearization for class D(B, C), where both B and C inherit from A. The merge step selects B first because it is the declared first base of D and is not a tail of any other candidate list; it then selects C, followed by A, and finally object. This order respects both the local precedence D(B, C) and the monotonicity rule that the MROs of B and C remain prefixes of D's MRO.","masteryContext":""},{"key":"C","isCorrect":false,"text":"(, , , , )","explanation":"C3 linearization must preserve the order in which base classes are written in the class statement: since D is defined as D(B, C), B must precede C in D's MRO. This option reverses that declaration order, which is what you would expect for D(C, B), not for the actual source code. It also wrongly places C's entire branch ahead of B's branch, directly contradicting the explicit base-class order.","masteryContext":""},{"key":"D","isCorrect":false,"text":"(, , , , )","explanation":"This order places A ahead of B and C even though A is only an indirect ancestor of D. In C3, a class must always be listed after its direct bases, and the direct bases of D—B and C—must appear in their declared order before any common ancestor like A is considered. This is a depth-first-style guess that puts the shared ancestor first, violating the local precedence constraint that C3 enforces and breaking the expected super() resolution path.","masteryContext":""}],"correctOptionKey":"B","correctOptions":["B"],"correctAnswerText":"","isMultiSelect":false,"mainExplanation":"Python 3 uses C3 linearization to compute the Method Resolution Order (MRO). For class D inheriting from B and C, which both inherit from A, the MRO is D, B, C, A, object. This satisfies the monotonicity and local precedence order: B comes before C (as per D's bases), and A is last among the user-defined classes, with object always appended.","examTrap":"Python Institute often tests whether candidates remember that