PCPP2 Practice Test 9 — 10 Questions

Question 1

Which object in SQLAlchemy is responsible for maintaining a collection of loaded objects and managing their lifecycle?

Accepted Answer

Session. The Session object acts as a workspace for objects and tracks their state.

Answer

Engine

Answer

Query

Answer

MetaData

Question 2

In the Chain of Responsibility pattern, how does a handler decide whether to pass a request to the next handler?

Accepted Answer

By calling the next handler's handle method only if it cannot fulfill the request. Each handler evaluates if it can process the request; if not, it calls the successor in the chain.

Answer

By querying the client for the next handler

Answer

By using an exception to jump to the next handler

Answer

By returning True from a base handler method

Question 3

Which THREE of the following are essential properties of a robust State pattern implementation?

Accepted Answer

The context should store the current state as a private member. State transitions, clear interface, and context awareness are essential.

Answer

The State interface should be as simple as possible

Answer

Every state should be a separate Singleton

Question 4

How do you retrieve the number of documents matched by a PyMongo 'find' operation without fetching all documents into memory?

Accepted Answer

collection.count_documents(filter). The count_documents() method on a collection is the recommended way to get a count.

Answer

cursor.count()

Answer

collection.size()

Answer

len(list(cursor))

Question 5

Which THREE methods are part of the PEP 249 Python DB-API 2.0 interface?

Accepted Answer

commit. execute, fetchone, and commit are standard parts of the DB-API specification.

Answer

get_json

Answer

filter_by

Question 6

You are implementing a Prototype pattern. What is the difference between shallow copy and deep copy in the context of cloning objects?

Accepted Answer

Shallow copy duplicates the reference, deep copy duplicates the object contents. A shallow copy creates a new object but references the same nested objects, while a deep copy recursively clones all nested objects.

Answer

Both copies result in the same memory address

Answer

Shallow copy clones nested objects, deep copy does not

Answer

Deep copy is always faster than shallow copy

Question 7

When implementing the Command pattern in Python, what is a primary advantage of using a 'Command' class hierarchy?

Accepted Answer

It allows commands to be queued, logged, or undone by the invoker. It allows commands to be treated as objects, which enables features like queuing, logging, and undo/redo.

Answer

It eliminates the need for functions

Answer

It automatically makes all operations thread-safe

Answer

It forces the application to use a specific GUI framework

Question 8

You need to dynamically add methods to a class at runtime. Which mechanism allows you to modify the class object before it is fully constructed?

Accepted Answer

Metaclasses. Metaclasses, specifically the __new__ method, allow for the modification of class creation.

Answer

Inheritance

Answer

Monkey patching

Answer

Class decorators

Question 9

Which magic method is used to define how an object is displayed for developers (for debugging)?

Accepted Answer

__repr__. __repr__ is the magic method used to provide an unambiguous string representation of an object.

Answer

__format__

Answer

__str__

Answer

__display__

Question 10

You need to implement a custom class that behaves like a sequence, allowing indexing and length checking. Which magic methods are required?

Accepted Answer

__getitem__ and __len__. To be a sequence, a class needs to implement __getitem__ and __len__.

Answer

__iter__ and __next__

Answer

__index__ and __size__

Answer

__setitem__ and __delitem__