PCPP2 Practice Test 3 — 30 Questions

Question 1

You want to store an object in a set. What must the object implement?

Accepted Answer

__hash__ and __eq__. To be hashable (and thus stored in a set), an object must implement __hash__ and have equality defined via __eq__.

Answer

__iter__

Answer

__set__

Answer

__init__ only

Question 2

Which THREE of the following are features of the 'threading' module in Python?

Accepted Answer

Semaphore objects. The threading module provides Locks, Semaphores, and Events for synchronization.

Answer

Shared memory between different processes

Answer

Automatic global interpreter lock removal

Question 3

When using the sqlite3 module, what is the primary purpose of using a context manager (the 'with' statement) on a connection object?

Accepted Answer

To automatically commit or rollback transactions.. In sqlite3, the connection context manager automatically commits or rolls back transactions.

Answer

To lock the database file for exclusive access.

Answer

To automatically close the connection upon exit.

Answer

To parse SQL queries for syntax errors.

Question 4

When using the MongoDB aggregation framework in PyMongo, which stage should be used to filter documents based on a condition?

Accepted Answer

$match. The $match stage is used to filter documents in an aggregation pipeline.

Answer

$group

Answer

$project

Answer

$filter

Question 5

In SQLAlchemy, how do you prevent an object from being saved to the database during a session.commit()?

Accepted Answer

session.expunge(obj). You can use session.expunge(obj) to remove the object from the session's management.

Answer

session.delete(obj)

Answer

session.detach(obj)

Answer

session.rollback()

Question 6

You are profiling your code and identify that a specific method is called millions of times. You decide to use a descriptor to optimize attribute access. What must the descriptor implement to intercept attribute assignment?

Accepted Answer

The __set__ method. A data descriptor is defined as an object that implements both __get__ and __set__ (or __delete__).

Answer

The __call__ method

Answer

The __init__ method

Answer

Only the __get__ method

Question 7

You are developing an application using SQLAlchemy and need to retrieve a single object by its primary key. Which method is preferred for this operation?

Accepted Answer

session.get(Model, pk). The get() method on the Session object is the optimized way to retrieve an object by its primary key.

Answer

Model.find(pk)

Answer

session.fetch(Model, pk)

Answer

session.query(Model).filter(Model.id == pk).first()

Question 8

You have a performance-critical application using heavy objects. You want to reduce memory footprint by preventing the creation of __dict__ for every instance. How should you proceed?

Accepted Answer

Define a __slots__ sequence attribute. Defining __slots__ in a class prevents the creation of __dict__ and __weakref__ for instances, significantly reducing memory usage.

Answer

Use a decorator to delete __dict__ after creation

Answer

Inherit from the object class exclusively

Answer

Set __dict__ = None in the class body

Question 9

Which THREE of the following are true about Python metaclasses?

Accepted Answer

Metaclasses are instances of 'type'. Metaclasses are types, they allow modifying class creation, and they are defined by inheriting from 'type'.

Answer

They are used to create instances directly

Answer

They are required for all classes in Python 3

Question 10

You are using a multiprocessing.Pool. Which method should you use to apply a function to a sequence of items and get the results back in order as they complete?

Accepted Answer

imap(). imap() returns an iterator that yields results in the order of the inputs.

Answer

apply()

Answer

map_async()

Answer

map()

Answer

starmap()

Question 11

You are using a multiprocessing.Semaphore(3). What happens when the 4th process attempts to acquire the semaphore?

Accepted Answer

It blocks until a slot is released.. The 4th process will block until one of the previous three processes releases the semaphore.

Answer

It creates a new process slot.

Answer

It raises an exception.

Answer

It bypasses the lock.

Answer

It is terminated by the OS.

Question 12

Which THREE of the following are standard ways to implement the 'Strategy' pattern in Python?

Accepted Answer

Injecting the strategy instance at runtime. Using functions, classes, or dependency injection are all valid strategies.

Answer

Hardcoding the strategy selection logic in the context

Answer

Using a global variable to change strategy behavior

Question 13

What is the result of using 'unittest.mock.patch.object' instead of 'unittest.mock.patch'?

Accepted Answer

It targets an attribute on an object instance.. patch.object is used to patch a specific attribute on an object, rather than patching an object by its string path.

Answer

It is faster.

Answer

It requires less memory.

Answer

It cannot be used with context managers.

Question 14

Which TWO of the following are valid ways to run tests?

Accepted Answer

python -m unittest. Both 'pytest' and 'python -m unittest' are the standard command-line ways to execute Python test suites.

Answer

unittest.execute()

Answer

python run_tests.py

Answer

import pytest; pytest.run()

Question 15

You are building an application using SSL/TLS. Which module must be used to wrap a standard socket to provide encrypted communication?

Accepted Answer

ssl. The ssl module provides the necessary wrappers to enable TLS/SSL over standard socket objects.

Answer

cryptography

Answer

hashlib

Answer

socket.ssl

Question 16

You are implementing a custom type in SQLAlchemy. Which method must be overridden to convert data from the database type back to a Python object?

Accepted Answer

process_result_value. The process_result_value method is responsible for type conversion during retrieval.

Answer

load_dialect_impl

Answer

bind_processor

Answer

process_bind_param

Question 17

Which TWO are common methods to handle BSON Date objects in PyMongo?

Accepted Answer

Using standard Python datetime objects. datetime.datetime objects are automatically converted to BSON Dates.

Answer

Using bson.datetime.Datetime

Answer

Using the 'timestamp' helper method

Answer

Using ISODate strings

Question 18

You are using the subprocess.run() function to execute an external command. Which argument ensures that the command's stdout is captured as a string rather than printed to the console?

Accepted Answer

capture_output=True. Setting capture_output=True automatically sets stdout and stderr to subprocess.PIPE.

Answer

text=True

Answer

stdout=True

Answer

shell=True

Answer

pipe=True

Answer

redirect=True

Question 19

When optimizing Python code, which tool should you use to identify hot spots in the execution path?

Accepted Answer

cProfile. cProfile is the standard built-in profiler in Python for identifying performance bottlenecks.

Answer

pydoc

Answer

pdb

Answer

unittest

Question 20

You are using sqlite3 in Python and need to ensure that data integrity is maintained when performing multiple related INSERT operations. Which method should you call on the connection object to commit your changes?

Accepted Answer

connection.commit(). The commit() method is used to save the current transaction to the database.

Answer

connection.save()

Answer

connection.flush()

Answer

cursor.apply()