PCPP1 Practice Test 4 — 10 Questions

Question 1

Which THREE of the following steps are required to initialize a TCP server socket?

Accepted Answer

Create a socket with socket.AF_INET and socket.SOCK_STREAM. A standard server lifecycle involves creating the socket, binding to an address/port, and listening for connections.

Answer

Call connect() to start the server

Answer

Call recv() before bind()

Question 2

When designing a class hierarchy, what is the best way to prevent a method from being overridden by subclasses?

Accepted Answer

Using the @final decorator from typing.. Python does not have a native 'final' keyword, but naming conventions (e.g., __method) or raising errors in the subclass can be used, though it is often discouraged in favor of clear documentation.

Answer

Defining it as a private method.

Answer

Defining it as a static method.

Answer

Using the 'final' keyword.

Question 3

You are using the socket module to create a TCP client. After creating the socket object, which method call is required to establish a connection to a remote server listening on 192.168.1.50 at port 8080?

Accepted Answer

sock.connect(('192.168.1.50', 8080)). The connect method is used on a client-side socket to initiate a TCP three-way handshake with a remote server.

Answer

sock.bind(('192.168.1.50', 8080))

Answer

sock.accept()

Answer

sock.listen(1)

Question 4

Which standard Python library module is used for lower-level networking and creating server/client sockets?

Accepted Answer

socket. The 'socket' module is the standard low-level interface to the network stack.

Answer

http.server

Answer

requests

Answer

networking

Question 5

When working with raw sockets, what does the 'socket.SOCK_STREAM' constant represent?

Accepted Answer

TCP connection-oriented sockets. SOCK_STREAM is used for TCP connections, which are connection-oriented and reliable.

Answer

UDP datagram sockets

Answer

Raw network sockets

Answer

Unix domain sockets only

Question 6

You are implementing the Observer pattern. Why should you avoid using a strong reference to the observers in the subject's list?

Accepted Answer

It prevents the observer from being garbage collected when it is no longer needed.. Strong references prevent garbage collection of the observers, leading to memory leaks if observers are meant to be temporary.

Answer

It causes circular dependency issues.

Answer

It makes the notify method thread-unsafe.

Answer

It violates the principle of encapsulation.

Question 7

If you define a class with a metaclass that has a custom __call__ method, when is that __call__ method executed?

Accepted Answer

When an instance of the class is created.. The metaclass's __call__ method is invoked whenever the class created by that metaclass is instantiated (i.e., when you call the class name like MyClass()).

Answer

Every time an instance method is called.

Answer

When the metaclass is first imported.

Answer

When the class itself is defined.

Question 8

What is the purpose of the 'weakref' module in relation to the Observer pattern?

Accepted Answer

To prevent memory leaks.. It allows the subject to maintain references to observers without preventing their collection by the garbage collector.

Answer

To allow private access to observers.

Answer

To ensure thread safety.

Answer

To serialize observers.

Question 9

Which magic method is triggered when an object is deleted using the 'del' keyword?

Accepted Answer

__del__. The __del__ method is called when the object's reference count reaches zero.

Answer

__clear__

Answer

__remove__

Answer

__destroy__

Question 10

Why does the __init__ method not return anything?

Accepted Answer

Because it is designed to initialize an existing instance.. The __init__ method is for initialization only; the object creation is handled by __new__.

Answer

Because of internal Python constraints.

Answer

To allow for multiple initialization.

Answer

Because it's a generator.