PCPP1 Practice Test 4 — 10 Questions

Question 1

A developer is writing a module-level variable that holds the maximum number of retries for a network client and will never change during runtime. Which naming convention does PEP 8 recommend for this constant?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Use all uppercase letters with underscores between words, such as `MAX_RETRIES`.. PEP 8 names constants using all uppercase letters with underscores separating words, so `MAX_RETRIES` is the recommended form. Python does not enforce immutability, but the naming convention communicates intent to readers and distinguishes constants from ordinary variables and classes. Other capitalizations belong to different categories of names.

Answer

Use CapWords, such as `MaxRetries`, to indicate that the value is a named entity.

Answer

Prefix the name with a single underscore, such as `_MAX_RETRIES`, to mark it as a constant.

Answer

Use lowercase letters with underscores, such as `max_retries`, because Python does not enforce constantness.

Question 2

A developer writes a class `Money` that implements `__eq__` to compare amounts and currencies, but does not implement `__hash__`. Instances of `Money` are then used as keys in a `set`. What is the result?

Accepted Answer

A TypeError is raised when adding an instance to the set because the class is unhashable.. Python disables the inherited `__hash__` when a class overrides `__eq__`, because equal objects must have equal hashes for hash-based collections to work correctly. The developer must define `__hash__` explicitly, hashing the same attributes used in `__eq__`, so that equal `Money` instances produce identical hashes and can be stored in sets or dicts.

Answer

Instances are hashed using the hash of their `__dict__`, so two equal `Money` objects collapse into one set element.

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The set stores instances by identity, so duplicates are allowed and no error occurs.

Answer

Instances can be added to a set, and equality is used for deduplication because `__hash__` defaults to `id()`-based hashing.

Question 3

Which TWO of the following statements about the Python 'requests' library are correct?

Accepted Answer

It uses 'urllib3' internally for connection pooling. Option A is correct because the requests library is built on top of urllib3, which provides the underlying connection pooling and HTTP transport capabilities. Option E is correct because when you call requests.get() or similar top-level functions without using a Session object, requests creates a temporary Session internally, performs the request, and then closes the connection rather than reusing it. Option B is incorrect because requests fully supports HTTPS and TLS/SSL verification. Option C is incorrect because requests is a third-party package that must be installed via pip, not part of the Python standard library. Option D is incorrect because requests is not guaranteed thread-safe for all operations; while Session objects can be used across threads with care, the library does not provide blanket thread-safety guarantees.

Answer

It does not support HTTPS

Answer

It is part of the standard library

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It is thread-safe by default for all operations

Question 4

You are using 'concurrent.futures.ThreadPoolExecutor' to fetch data from multiple REST APIs. What happens if an exception is raised inside a thread?

Accepted Answer

The exception is stored and raised when calling future.result(). Exceptions raised in a future are captured and re-raised when calling result() on the Future object returned by submit().

Answer

The exception is ignored by the ThreadPoolExecutor

Answer

The entire program crashes immediately

Answer

The thread dies silently without notification

Question 5

Which TWO of the following statements correctly describe the behavior of the Tkinter 'pack' geometry manager?

Accepted Answer

The 'side' parameter can be set to 'top', 'bottom', 'left', or 'right'.. Option B is correct because pack()'s 'side' parameter accepts exactly the four values 'top', 'bottom', 'left', and 'right', which determine the edge of the container against which the widget is packed (defaulting to 'top'). Option E is correct because the 'fill' parameter accepts 'x', 'y', 'both', or 'none', controlling whether the widget stretches to fill available space along the horizontal axis, vertical axis, both, or neither. Option A is wrong because pack() honors call order: widgets are allocated space in the sequence pack() is invoked, so order directly affects layout. Option C is wrong because the grid coordinate system belongs to the grid() geometry manager, not pack(). Option D is wrong because absolute X/Y positioning is the domain of the place() geometry manager, whereas pack() uses relative cavity-based allocation.

Answer

The manager automatically ignores the order in which pack() is called.

Answer

Widgets are placed in a grid coordinate system.

Answer

Widgets are positioned at exact X and Y coordinates.

Question 6

Which THREE of the following are valid ways to pass arguments to a function called by a Tkinter button command?

Accepted Answer

command=lambda arg=arg1: my_func(arg). Option A is correct because a lambda with a default argument (arg=arg1) captures the value at definition time and passes it to my_func when the button is clicked, avoiding late-binding issues. Option B is correct because a zero-argument lambda that closes over arg1 defers execution of my_func(arg1) until the button is pressed, which is the standard Tkinter pattern for passing arguments. Option C is correct because functools.partial(my_func, arg1) creates a callable that already has arg1 bound, and Tkinter accepts any callable as the command. Option D is wrong because my_func(arg1=value) is invoked immediately at widget creation, so command receives the function's return value rather than a callable. Option E is wrong for the same reason: my_func(arg1) executes right away and its result is assigned to command, not deferred until the button is clicked.

Answer

command=my_func(arg1=value)

Answer

command=my_func(arg1)

Question 7

Which TWO of the following are valid ways to create a singleton in Python?

Accepted Answer

Using a base class with a custom __new__ method.. Option C is correct because overriding __new__ in a base class lets you intercept instance creation and return the same cached instance every time, which is the canonical Python idiom for enforcing a single instance. Option E is correct because Python modules are imported only once and cached in sys.modules, so module-level state and functions naturally behave as a singleton. Option A is wrong because an uninitialized global variable provides no instance at all and no control over creation. Option B is wrong because returning a new instance on every call is the opposite of the singleton pattern. Option D is wrong because a plain class with no special methods creates a fresh object on each instantiation.

Answer

Using a global variable that is not initialized.

Answer

Using a function that returns a new instance every call.

Answer

Using a standard class without any special methods.

Question 8

Which TWO of the following are valid conventions for naming in Python according to PEP 8?

Accepted Answer

Classes: PascalCase. Option B is correct because PEP 8 specifies that class names should use the CapWords (PascalCase) convention, e.g., class MyClass. Option E is correct because PEP 8 states that variable names should be lowercase with words separated by underscores (snake_case), e.g., my_variable. The unmarked options are incorrect: constants should be UPPER_CASE_WITH_UNDERSCORES, not camelCase (A); modules should be short, all-lowercase names, preferably with underscores, not PascalCase (C); and functions should be lowercase with underscores (snake_case), not camelCase (D).

Answer

Constants: camelCase

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Modules: PascalCase

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Functions: camelCase

Question 9

Which widget is most suitable for displaying multi-line, editable text?

Accepted Answer

tk.Text(). tk.Text is the Tkinter widget designed for multi-line, editable text input, supporting scrolling, indexing, tags, and embedded windows/images. It is the correct choice when users need to enter or edit paragraphs of text. Entry and Label are single-line or read-only, and Listbox is for selecting items from a list.

Answer

tk.Listbox()

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tk.Entry()

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tk.Label()

Question 10

What is the difference between a class-level variable and an instance-level variable?

Accepted Answer

Class-level variables are shared by all instances.. A class-level variable is shared across all instances of the class, whereas an instance-level variable is specific to each object.

Answer

Instance-level variables cannot be modified.

Answer

Class-level variables are always constant.

Answer

Class-level variables are hidden from subclasses.