- A
`def from_string(self, s):\n parts = s.split(',')\n return Point(int(parts[0]), int(parts[1]))`
Why wrong: This is an instance method; it would require an existing instance to call, which is not the intent.
- B
`@staticmethod\ndef from_string(s):\n parts = s.split(',')\n return Point(int(parts[0]), int(parts[1]))`
Why wrong: Using `@staticmethod` and hardcoding `Point` prevents the method from being inherited properly.
- C
`def from_string(cls, s):\n parts = s.split(',')\n return cls(int(parts[0]), int(parts[1]))`
Why wrong: Without `@classmethod`, the first parameter will be `self` (an instance), not the class.
- D
`@classmethod\ndef from_string(cls, s):\n parts = s.split(',')\n return cls(int(parts[0]), int(parts[1]))`
This correctly uses `@classmethod` and calls `cls` to create a new instance.
Quick Answer
The correct answer is the snippet using `@classmethod` with `cls` as the first parameter, because a class method alternative constructor must receive the class itself via `cls` and then call `cls(...)` to create a new instance. This pattern is the standard Python idiom for defining alternative constructors, as the `@classmethod` decorator binds the method to the class rather than to an instance, allowing you to parse external data—like the string "10,20"—and return a properly initialized object. On the Certified Associate Python Programmer PCAP exam, this question tests your understanding of class methods as factory functions, a common topic in the "Object-Oriented Programming" domain. A frequent trap is confusing `@classmethod` with `@staticmethod`; remember that a static method lacks access to `cls` and cannot create instances of the class. Memory tip: think "class method builds the class" — the `cls` parameter is your constructor key.
PCAP Object-Oriented Programming Practice Question
This PCAP practice question tests your understanding of object-oriented programming. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A programmer uses a class method to create an alternative constructor for a `Point` class. The method should parse a string like "10,20" and return a `Point` instance with x=10, y=20. Which code snippet correctly implements this?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
`@classmethod\ndef from_string(cls, s):\n parts = s.split(',')\n return cls(int(parts[0]), int(parts[1]))`
A class method receives the class as the first argument (`cls`) and can be used to create instances via `cls(...)`. The `@classmethod` decorator is required.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
`def from_string(self, s):\n parts = s.split(',')\n return Point(int(parts[0]), int(parts[1]))`
Why it's wrong here
This is an instance method; it would require an existing instance to call, which is not the intent.
- ✗
`@staticmethod\ndef from_string(s):\n parts = s.split(',')\n return Point(int(parts[0]), int(parts[1]))`
Why it's wrong here
Using `@staticmethod` and hardcoding `Point` prevents the method from being inherited properly.
- ✗
`def from_string(cls, s):\n parts = s.split(',')\n return cls(int(parts[0]), int(parts[1]))`
Why it's wrong here
Without `@classmethod`, the first parameter will be `self` (an instance), not the class.
- ✓
`@classmethod\ndef from_string(cls, s):\n parts = s.split(',')\n return cls(int(parts[0]), int(parts[1]))`
Why this is correct
This correctly uses `@classmethod` and calls `cls` to create a new instance.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PCAP NAT questions on configuration and troubleshooting.
- →
Object-Oriented Programming — study guide chapter
Learn the concepts, then practise the questions
- →
Object-Oriented Programming practice questions
Targeted practice on this topic area only
- →
All PCAP questions
511 questions across all exam domains
- →
Certified Associate Python Programmer PCAP study guide
Full concept coverage aligned to exam objectives
- →
PCAP practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related PCAP practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Modules and Packages practice questions
Practise PCAP questions linked to Modules and Packages.
Strings practice questions
Practise PCAP questions linked to Strings.
Object-Oriented Programming practice questions
Practise PCAP questions linked to Object-Oriented Programming.
Exceptions and File I/O practice questions
Practise PCAP questions linked to Exceptions and File I/O.
PCAP fundamentals practice questions
Practise PCAP questions linked to PCAP fundamentals.
PCAP scenario practice questions
Practise PCAP questions linked to PCAP scenario.
PCAP troubleshooting practice questions
Practise PCAP questions linked to PCAP troubleshooting.
Practice this exam
Start a free PCAP practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this PCAP question test?
Object-Oriented Programming — This question tests Object-Oriented Programming — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: `@classmethod\ndef from_string(cls, s):\n parts = s.split(',')\n return cls(int(parts[0]), int(parts[1]))` — A class method receives the class as the first argument (`cls`) and can be used to create instances via `cls(...)`. The `@classmethod` decorator is required.
What should I do if I get this PCAP question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related PCAP NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 24, 2026
This PCAP practice question is part of Courseiva's free Python Institute certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCAP exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.