PCPP2 Practice Test 12 — 15 Questions

Question 1

Which of the following best describes the benefit of using parameterized queries in sqlite3?

Accepted Answer

They prevent SQL injection attacks.. Parameterized queries prevent SQL injection by separating the query logic from the data.

Answer

They allow for multiple database connections.

Answer

They improve query execution speed by pre-compiling.

Answer

They automatically format the output as JSON.

Question 2

You are designing a State pattern. Which component is responsible for changing the state of the context object?

Accepted Answer

The concrete state objects. Either the Context or the State objects themselves can transition the state, but encapsulating the transition logic inside the concrete state objects is typical for complex state flows.

Answer

The abstract state base class

Answer

A separate controller object

Answer

The client code

Question 3

When connecting to a MongoDB instance using PyMongo, what is the role of the 'MongoClient' object?

Accepted Answer

It serves as the main connection handle to the MongoDB cluster.. The MongoClient acts as the entry point to the MongoDB server, allowing access to databases and collections.

Answer

It stores individual documents in memory.

Answer

It defines the schema for BSON documents.

Answer

It translates SQL queries into MQL.

Question 4

Which TWO of these are valid parameters for the MongoClient constructor?

Accepted Answer

host. MongoClient accepts host and port, or a connection string.

Answer

table_prefix

Answer

use_sql

Answer

cache_size

Question 5

In the Observer pattern, what is the best way to prevent memory leaks when the Subject maintains a list of Observers?

Accepted Answer

Use the weakref module to store references to the Observers. If the Subject maintains strong references to Observers, they cannot be garbage collected. Using weak references allows them to be collected when no longer used elsewhere.

Answer

Use a global list of observers to manage them centrally

Answer

Set the Observer list to None after every notification cycle

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Explicitly call the detach method for every Observer

Question 6

In the Decorator pattern, why is it preferred to use the functools.wraps decorator when creating a function decorator?

Accepted Answer

It preserves the metadata of the original function. functools.wraps preserves the metadata (like __name__ and __doc__) of the original function, which is critical for debugging and reflection.

Answer

It automatically implements the Singleton pattern

Answer

It prevents the decorator from being applied multiple times

Answer

It ensures the function runs faster

Question 7

Which pattern is most appropriate for a scenario where you want to provide a standard interface for a suite of related or dependent objects without specifying their concrete classes?

Accepted Answer

Abstract Factory. The Abstract Factory pattern provides an interface for creating families of related objects.

Answer

Proxy

Answer

Singleton

Answer

Builder

Question 8

Which TWO of the following are true about the Template Method pattern?

Accepted Answer

The base class defines the skeleton of an algorithm. It provides a skeleton algorithm and allows subclasses to override steps.

Answer

It forces the use of multiple inheritance

Answer

Subclasses are not allowed to override any methods

Answer

It is a Creational pattern

Question 9

Which TWO of the following are true about the 'descriptor protocol' in Python?

Accepted Answer

A descriptor is a class that implements __get__, __set__, or __delete__. Descriptors define __get__, __set__, or __delete__, and they allow objects to customize attribute access.

Answer

Descriptors must be defined inside a metaclass

Answer

Descriptors are only used for methods

Answer

Descriptors automatically make an object serializable

Question 10

Which Python design principle is most strongly supported by the Adapter pattern?

Accepted Answer

Open/Closed Principle. The Adapter pattern allows incompatible interfaces to work together, promoting the Open/Closed Principle by allowing new adapters without changing existing code.

Answer

Single Responsibility Principle

Answer

Dependency Inversion Principle

Answer

Liskov Substitution Principle

Question 11

Which of the following is true regarding daemon threads in Python?

Accepted Answer

They are abruptly terminated when the main process exits.. Daemon threads are terminated abruptly when the main program exits, which can lead to incomplete operations.

Answer

They are only used for system-level tasks.

Answer

They are guaranteed to finish before the program ends.

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They use more memory than regular threads.

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They cannot create child threads.

Question 12

When configuring a connection pool in SQLAlchemy, what does the 'pool_size' parameter define?

Accepted Answer

Number of persistent connections kept in the pool.. pool_size defines the number of persistent connections to keep open in the pool.

Answer

The number of retries before failure.

Answer

The timeout duration for queries.

Answer

Maximum number of simultaneous sessions.

Question 13

Which THREE are characteristics of BSON (Binary JSON) as used by MongoDB?

Accepted Answer

It is optimized for efficient traversal. BSON is binary-encoded, supports more types than JSON, and is optimized for traversal.

Answer

It is deprecated in newer MongoDB versions

Answer

It is exactly the same as JSON

Question 14

Which THREE design patterns are considered 'Behavioral' patterns?

Accepted Answer

Strategy. Observer, Command, and Strategy are all classic Behavioral patterns.

Answer

Proxy

Answer

Singleton

Question 15

What is the purpose of the socket.recvfrom() method?

Accepted Answer

It retrieves data and the sender's address in a single call.. recvfrom() is designed for connectionless protocols like UDP to receive data and return the address of the sender.

Answer

It is for TCP servers to accept new connections.

Answer

It forces a socket to switch to UDP mode.

Answer

It is used to receive large files in chunks.