PCPP1 Practice Questions 2 — 50 Questions

Question 1

In the Factory pattern, what should you do if the requested type is unknown?

Accepted Answer

Raise a ValueError.. Raising a ValueError or a custom 'UnknownTypeException' is the standard way to handle invalid inputs in a factory.

Answer

Log the error and return the base class.

Answer

Return a default instance.

Answer

Return None.

Question 2

You are designing a Python application that consumes a REST API which returns JSON data. The API responses can be large, and you need to process the JSON incrementally to avoid loading the entire response into memory. The server supports chunked transfer encoding. Which of the following techniques should you use with the 'requests' library to stream the response and parse it incrementally?

Accepted Answer

Set stream=True in the request and use response.iter_content() to read chunks, then parse each chunk with a streaming JSON parser like ijson.. To process large JSON responses incrementally with 'requests', you must enable streaming with 'stream=True' and then read the response in chunks using 'response.iter_content()'. Since JSON is not inherently line-delimited, you need a streaming parser like 'ijson' to parse the chunks as they arrive. This avoids loading the entire response into memory, making it suitable for large datasets.

Answer

Use response.json() directly; it automatically streams and parses the JSON without loading everything into memory.

Answer

Use requests.get() with a large timeout and rely on the operating system's memory management to handle the response.

Answer

Set stream=True and then call response.json() to parse the streamed data.

Question 3

You are implementing a REST API client in Python using the 'requests' library. The API requires authentication using OAuth 2.0. You need to obtain an access token and then use it to authenticate subsequent requests. Which TWO of the following statements about handling OAuth 2.0 with 'requests' are correct? (Choose two.)

Accepted Answer

You can use the 'requests-oauthlib' library to handle the OAuth 2.0 flow, including token refresh.. Handling OAuth 2.0 with 'requests' typically involves either using a specialized library like 'requests-oauthlib' for full flow management, or manually adding the Bearer token to the Authorization header if you already have a valid token. The core 'requests' library does not provide built-in OAuth 2.0 support, and sending tokens as query parameters is insecure and not recommended.

Answer

OAuth 2.0 access tokens are typically sent as query parameters in the URL.

Answer

The 'requests' library automatically refreshes expired OAuth 2.0 tokens when using the 'auth' parameter.

Answer

The 'requests' library includes built-in support for OAuth 2.0 token management.

Question 4

Which TWO of the following are secure coding practices in Python?

Accepted Answer

Avoid using 'pickle' for untrusted data.. Option C is correct because Python's 'pickle' module is inherently unsafe for untrusted data: unpickling executes arbitrary code via the __reduce__ method, so deserializing attacker-controlled bytes can lead to remote code execution; safe alternatives include 'json' or other non-executable formats. Option D is correct because validating and sanitizing all user input (e.g., using allowlists, type checks, and parameterized queries) prevents injection flaws such as SQL injection, command injection, and XSS, forming a core secure coding practice. Option A is wrong because 'subprocess' with 'shell=True' passes the command through the shell, enabling shell metacharacter injection; the safe practice is 'shell=False' with an argument list. Option B is wrong because 'eval()' executes arbitrary Python expressions and is a classic code-injection vector; dynamic execution should use safer mechanisms like 'ast.literal_eval' for literals. Option E is wrong because hardcoded credentials in source code expose secrets and violate secure secret-management practices such as using environment variables or a secrets manager.

Answer

Use 'subprocess' with 'shell=True'.

Answer

Always use 'eval()' for dynamic execution.

Answer

Use hardcoded credentials for database connections.

Question 5

Which TWO of these identify a potential 'code smell' in Python exception handling?

Accepted Answer

Swallowing exceptions with an empty 'except' block.. Option B is a code smell because an empty 'except:' block silently swallows every exception, hiding failures and making debugging nearly impossible; at minimum the handler should log or re-raise. Option D is a code smell because 'BaseException' includes 'SystemExit', 'KeyboardInterrupt', and 'GeneratorExit', so catching it can prevent normal interpreter shutdown and interrupt handling; application code should normally catch 'Exception' or more specific subclasses. Option A is not a smell: 'finally' is the correct construct for guaranteed cleanup such as closing files or releasing locks. Option C is not a smell: catching specific exception types is the recommended practice for precise, safe error handling. Option E is not a smell: defining and raising custom exceptions improves clarity and lets callers handle domain-specific errors.

Answer

Using 'finally' for cleanup.

Answer

Catching specific exceptions.

Answer

Raising custom exceptions.

Question 6

Which function is used to check if an object is an instance of a class?

Accepted Answer

isinstance(). isinstance(obj, Class) is the standard way to check inheritance.

Answer

hasattr()

Answer

issubclass()

Answer

type()

Question 7

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

Accepted Answer

TCP connection-oriented sockets. socket.SOCK_STREAM designates a reliable, connection-oriented byte stream, which in practice maps to TCP (or a Unix-domain stream socket). The Python socket module passes this constant to socket() to select the transport semantics, so SOCK_STREAM sockets guarantee ordered, error-checked delivery via the TCP three-way handshake. This is why HTTP, SMTP, and SSH clients built on Python sockets use SOCK_STREAM.

Answer

UDP datagram sockets

Answer

Raw network sockets

Answer

Unix domain sockets only

Question 8

You are building a custom HTTP client and need to handle persistent connections (keep-alive). What is the primary role of the 'Connection' header?

Accepted Answer

To request the reuse of the TCP connection. The 'Connection: keep-alive' header tells the server that the client wants to reuse the same TCP connection for multiple requests.

Answer

To signal that the server is alive

Answer

To encrypt the connection

Answer

To set the timeout for the connection

Question 9

How do you properly handle a non-200 status code when using 'requests' if you want to avoid manual status code checking?

Accepted Answer

Use response.raise_for_status(). Calling response.raise_for_status() will raise an HTTPError exception if the status code indicates an error (4xx or 5xx).

Answer

Use a decorator on the request function

Answer

Check response.error

Answer

The library raises an exception by default

Question 10

A Python developer is writing a function that reads a configuration file and returns a dictionary. They want to follow PEP 8 and best practices for function design and documentation. Which two of the following should they do? (Choose two.)

Accepted Answer

Include a docstring that describes the function's purpose, parameters, and return value.. Following PEP 8 and best practices, function names should be descriptive and use lowercase with underscores, and public functions should have docstrings that explain their purpose, parameters, and return values. These practices enhance code readability and maintainability. The other options either use unclear parameter names, raise overly broad exceptions, or misplace the function relative to imports, all of which violate established conventions.

Answer

Place the function at the top of the file, before any imports, to make it easily accessible.

Answer

Raise a generic `Exception` if the file cannot be read, to keep error handling simple.

Answer

Use a single-letter parameter name like `f` for the file path to keep the signature short.

Question 11

You are processing a CSV file using csv.DictReader. If your input file lacks a header row, how do you provide the field names?

Accepted Answer

csv.DictReader(f, fieldnames=['a', 'b']). You pass the 'fieldnames' argument to the constructor to define the headers explicitly.

Answer

csv.DictReader(f, headers=['a', 'b'])

Answer

csv.DictReader(f).map(['a', 'b'])

Answer

csv.DictReader(f, columns=['a', 'b'])

Question 12

You are developing a Tkinter application that includes a Canvas widget for drawing a dynamic bar chart. The chart data updates every second, and you must redraw the bars. To avoid visual flicker and improve performance, you decide to reuse existing canvas items instead of deleting and recreating them. Which Canvas method should you use to change the height of an existing rectangle item identified by its item ID?

Accepted Answer

canvas.coords(item_id, x1, y1, x2, y2). To dynamically update the size of an existing canvas item, you should modify its coordinates. The coords() method allows you to set new coordinates for an item, effectively resizing or repositioning it without deleting and recreating. This is efficient and avoids flicker. Other methods like itemconfig() are for changing options like fill, move() only translates, and scale() applies proportional scaling, which is not ideal for precise height adjustments.

Answer

canvas.move(item_id, 0, delta_y)

Answer

canvas.scale(item_id, x_origin, y_origin, x_scale, y_scale)

Answer

canvas.itemconfig(item_id, height=new_height)

Question 13

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 14

Which method is used to customize the behavior of the 'in' operator?

Accepted Answer

__contains__. The __contains__ method is called when using the 'in' or 'not in' operators.

Answer

__has__

Answer

__find__

Answer

__in__

Question 15

When using the __call__ method to implement a decorator, what does the decorator receive as an argument?

Accepted Answer

The function to be decorated.. The decorator receives the function object that is being decorated as the argument to the constructor (if the decorator is a class instance) or directly if it is a function.

Answer

The arguments to the function.

Answer

The instance of the class.

Answer

The class object.

Question 16

How do you correctly call a method from a sibling class in a diamond inheritance structure using super()?

Accepted Answer

Use super() in each class to delegate to the next class in the MRO.. super() follows the Method Resolution Order (MRO), which correctly handles diamond inheritance by delegating calls to the next class in the chain, not just the parent.

Answer

Call the grandparent class directly.

Answer

Use the __bases__ attribute to iterate through parents.

Answer

Explicitly call the sibling class method by name.

Question 17

Which magic method is responsible for providing the informal string representation of an object, typically used for user-facing output?

Accepted Answer

__str__. The __str__ method is used for informal, readable string representations, whereas __repr__ is for formal, unambiguous representations.

Answer

__format__

Answer

__unicode__

Answer

__repr__

Question 18

Why does the 'abc' module provide the 'ABCMeta' metaclass?

Accepted Answer

To enforce abstract method implementation at instantiation.. ABCMeta is the metaclass that implements the logic to prevent instantiation of classes with abstract methods.

Answer

To allow private methods.

Answer

To improve method resolution speed.

Answer

To support multiple inheritance.

Question 19

Which magic method enables index access (e.g., obj[i])?

Accepted Answer

__getitem__. The __getitem__ method allows an object to support indexing.

Answer

__index__

Answer

__setitem__

Answer

__access__

Question 20

When naming a constant in Python, which convention does PEP 8 recommend?

Accepted Answer

UPPER_CASE_WITH_UNDERSCORES.. Constants should be named using all capital letters with underscores to separate words.

Answer

PascalCase.

Answer

snake_case.

Answer

CamelCase.