PCAP Practice Test 6 — 10 Questions

Question 1

Consider the following code: class A: x = 1; class B(A): pass; class C(A): x = 2; class D(B, C): pass. What is D.x?

Accepted Answer

2. Python's method resolution order (MRO) for class D, which uses multiple inheritance, follows the C3 linearization algorithm. The MRO for D is D, B, C, A, and since C defines x = 2, that attribute overrides the x = 1 from A in the inheritance chain, so D.x resolves to 2.

Answer

AttributeError

Answer

1

Answer

(1, 2) tuple

Question 2

Which TWO of the following are appropriate techniques for logging exception details in Python? (Select exactly 2)

Accepted Answer

Using traceback.format_exc(). `traceback.format_exc()` returns the full traceback as a string, which can be logged or printed to capture detailed exception context. Option E is correct because `logging.exception()` automatically includes the traceback of the current exception when called inside an `except` block, making it the idiomatic way to log exceptions in Python.

Answer

Using print(e.args)

Answer

Using sys.exc_info()

Answer

Using raise without argument

Question 3

Which THREE are valid escape sequences in Python strings?

Accepted Answer

. 
 is a standard escape sequence in Python that represents a newline character (ASCII LF, 0x0A). It is defined in the Python language specification and is commonly used to insert line breaks in string literals.

Answer

\q

Answer

\z

Question 4

Which THREE of the following are true about Python's exception hierarchy?

Accepted Answer

KeyboardInterrupt inherits from BaseException.. `KeyboardInterrupt` inherits directly from `BaseException`, not from `Exception`. This design ensures that `KeyboardInterrupt` (raised by Ctrl+C) is not caught by a generic `except Exception:` clause, allowing the program to be interrupted even when broad exception handling is in place.

Answer

IOError is a separate class from OSError.

Answer

GeneratorExit inherits from Exception.

Question 5

Match each Python built-in function to its description.

Accepted Answer

len(): Returns the length (number of items) of an iterable.. The correct matches are: len() returns length, map() applies a function, filter() filters by truth, zip() combines iterables. Common confusions involve swapping the definitions of map and len, or filter and zip.

Answer

len(): Applies a function to every item of an iterable and returns a map object.

Answer

map(): Returns the length (number of items) of an iterable.

Question 6

A developer is writing a package that contains multiple modules. The package should allow users to import it directly and have all commonly used functions available at the package level. For example, after `import mypackage`, the user should be able to call `mypackage.func1()` without needing to import submodules. Which is the best way to achieve this?

Accepted Answer

In `__init__.py`, import the desired functions from the submodules, e.g., `from .submodule import func1`.. `__init__.py` is executed when a package is imported, and importing functions from submodules into `__init__.py` makes them directly accessible as attributes of the package object. This allows `mypackage.func1()` to work without requiring the user to import submodules explicitly, satisfying the requirement of a flat namespace at the package level.

Answer

Create a wrapper function in `__init__.py` that delegates calls to the submodule functions.

Answer

Include `__all__` in each submodule and ensure `__init__.py` is empty.

Answer

Define a list named `__all__` in the package's `__init__.py` that lists the functions.

Question 7

Given that MyClass defines __private_attr in __init__, why does this error occur?

Accepted Answer

The attribute name is mangled to _MyClass__private_attr.. Python uses name mangling for attributes with double underscores (__) to avoid accidental overriding in subclasses. When you define __private_attr inside __init__, Python internally renames it to _MyClass__private_attr. Attempting to access obj.__private_attr from outside the class fails because that mangled name is not recognized, leading to an AttributeError.

Answer

The attribute was not defined in __init__.

Answer

Private attributes cannot be accessed outside the class.

Answer

The attribute is a class attribute not an instance attribute.

Question 8

Your company has two separate Python packages: 'app' and 'lib'. They are maintained by different teams. 'app' depends on 'lib', but 'lib' is still under development and its API changes frequently. To avoid breaking 'app', the team decides to use a virtual environment and install a specific version of 'lib'. However, during development, they need to test 'app' with the latest 'lib' changes from the Git repository. The current workflow is: (1) activate virtual env, (2) install 'lib' from local source using `pip install -e /path/to/lib`. This installs 'lib' as a development package. But one developer reports that after pulling latest 'lib' changes, importing 'lib' in 'app' still uses the old version even after re-running pip install -e. What is the most likely reason?

Accepted Answer

The editable install may still point to an old copy of the library if the source directory was moved or if there is a stray .egg-link file.. The most likely reason is D. When using `pip install -e` (editable install), pip creates a special `.egg-link` file (or similar pointer) in the site-packages directory that points to the source directory. If the source directory was moved, renamed, or if a stale `.egg-link` file remains from a previous install, pip may still reference the old location, causing the old version to be imported even after re-running the install command. This is a known subtlety of editable installs, especially when the source code is managed under version control and the directory structure changes.

Answer

Python caches imported modules in sys.modules, so importing again does not reload the module from disk.

Answer

The package 'lib' is being imported as a namespace package, so changes are not picked up.

Answer

The .pyc files are not being invalidated because the timestamps are not updated.

Question 9

You are developing a package 'analytics' that contains subpackages 'stats' and 'ml'. The __init__.py of 'analytics' imports a function 'normalize' from 'analytics.stats'. When a user runs `import analytics`, they get an ImportError. Which change ensures the package imports correctly?

Accepted Answer

Change the import in analytics/__init__.py to: from .stats import normalize. It uses an explicit relative import (`from .stats import normalize`), which is the proper way to import from a subpackage within a package. Absolute imports like `from analytics.stats import normalize` can fail if the package's parent directory is not in `sys.path`, which is common when running scripts directly. Relative imports resolve correctly based on the package structure, ensuring the import works regardless of how the package is invoked.

Answer

Change the import to: from stats import normalize

Answer

Add sys.path.append('.') before the import in __init__.py

Answer

Move the import statement to the stats/__init__.py file

Question 10

A programmer writes a function that expects a string and returns it reversed. Which code snippet correctly reverses the string 'stressed' to 'desserts'?

Accepted Answer

result = s[::-1]. Both option B and option D correctly reverse the string 'stressed' to 'desserts'. Option B uses slice notation `[::-1]`, which creates a reversed copy of the string by stepping from end to start with a step of -1. This is the most direct and idiomatic way to reverse a string in Python. Option D uses `''.join(reversed(s))`: `reversed(s)` returns an iterator that yields characters in reverse order, and `join()` concatenates them into a new string. This is also a valid and correct approach. Option A is incorrect because strings do not have a `reversed()` method; `reversed()` is a built-in function. Option C is incorrect because `.reverse()` is a list method, not a string method, and strings are immutable.

Answer

result = s.reversed()

Answer

s.reverse()