PCAP Practice Test 13 — 15 Questions

Question 1

A developer generates a report where numbers must be right-aligned in a 10-character column using f-strings: f'{value:>10}'. However, some values may be None, causing a TypeError. Which is the most robust way to handle None values without affecting other falsy values like 0?

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

Accepted Answer

f'{value if value is not None else "N/A":>10}'. It uses an explicit identity check (`value is not None`) to distinguish `None` from other falsy values like `0` or empty strings. This ensures that `0` is still right-aligned as a number, while `None` is replaced with the string `"N/A"` before formatting. The f-string then applies the `>10` alignment specifier to the resulting value.

Answer

Use str.format() with a conditional for the format spec

Answer

f'{value or "N/A":>10}'

Answer

Wrap the f-string in a try-except block

Question 2

A developer creates a package named 'mypkg' with an __init__.py file. Inside the package, there is a module 'utils.py'. Which of the following is the correct way to import the function 'helper' from 'utils' from outside the package?

Accepted Answer

from mypkg.utils import helper. It uses the standard Python syntax for importing a specific name from a submodule within a package: `from package.module import name`. This directly imports the `helper` function into the current namespace, making it callable without any prefix. The `__init__.py` file marks `mypkg` as a package, and `utils.py` is a module inside it, so `from mypkg.utils import helper` is the proper way to access `helper` from outside the package.

Answer

import mypkg.utils.helper

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import mypkg; mypkg.utils.helper

Answer

from mypkg import utils.helper

Question 3

A class defines an __init__ method that takes optional arguments. What is the correct way to provide default values?

Accepted Answer

Use default parameter values in the __init__ signature.. Python's `__init__` method, like any other function, supports default parameter values in its signature. This is the idiomatic and simplest way to provide default values for instance attributes, as the defaults are evaluated at function definition time and assigned to the parameter when no argument is provided.

Answer

Use class variables to store defaults.

Answer

Override __new__ to set default values.

Answer

Use a separate setter method called after instantiation.

Question 4

Which method returns the lowest index where a specified substring is found, or -1 if not found?

Accepted Answer

find(). The `find()` method in Python returns the lowest index where the specified substring is found within the string, or -1 if the substring is not present. This behavior directly matches the question's requirement, making option A correct.

Answer

locate()

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search()

Answer

index()

Question 5

Which THREE factors influence Python's module search path (sys.path)?

Accepted Answer

The site-packages directory where pip installs packages. The site-packages directory is automatically included in sys.path by the site module during Python's initialization. This directory is the default location where pip installs third-party packages, making them importable without manual path manipulation.

Answer

The HOME environment variable

Answer

The current working directory at runtime

Question 6

A class has both `@classmethod` and `@staticmethod` decorators. What is a key difference between them?

Accepted Answer

A classmethod receives the class as first argument.. The key difference is that a `@classmethod` receives the class itself as the first implicit argument (conventionally named `cls`), allowing it to access or modify class-level state, while a `@staticmethod` receives no implicit first argument and behaves like a plain function, unable to access the class or instance. This makes option B correct because it accurately describes the distinguishing feature of a classmethod.

Answer

A classmethod cannot be called on an instance.

Answer

A staticmethod must be called from the class only.

Answer

A classmethod cannot access class variables.

Question 7

What is the result of 'abcdef'[::-2]?

Accepted Answer

'fdb'. The slicing syntax [::-2] means start from the end (default step negative), go to the beginning, and take every second character in reverse order. For 'abcdef', starting at 'f' (index -1), then skipping one to 'd' (index -3), then 'b' (index -5), resulting in 'fdb'. Option C is correct.

Answer

'dfb'

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'ace'

Answer

'eca'

Question 8

A developer wants to convert a string 'Python' to all uppercase letters. Which string method should be used?

Accepted Answer

upper(). The `upper()` method returns a copy of the string with all lowercase characters converted to uppercase. Since the goal is to convert 'Python' to 'PYTHON', `upper()` is the correct and most direct method for this task.

Answer

capitalize()

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title()

Answer

swapcase()

Question 9

An application uses a class to represent a configuration object that reads settings from a file. The class has a class attribute config_cache that holds a dictionary of loaded configurations to avoid repeated file reads. However, the developer notices that when they modify the dictionary for one instance, it affects all instances. They want to ensure that each instance has its own copy of the configuration data upon initialization. Which change should they make?

Accepted Answer

Move the dictionary initialization into the __init__ method so each instance creates its own dictionary.. Moving the dictionary initialization into the __init__ method ensures that each instance gets its own separate dictionary object. Class attributes are shared across all instances, so modifying the dictionary via one instance changes it for all. By assigning `self.config_cache = {}` inside __init__, each instance creates a new, independent dictionary upon instantiation, solving the shared-state problem.

Answer

Use a @staticmethod to return a new dictionary each time.

Answer

Keep the class attribute but use a deep copy in __init__ before modifying.

Answer

Define the dictionary inside a class method.

Question 10

Which TWO of the following are special methods in Python?

Accepted Answer

`__init__`. `__init__` is a predefined special method in Python used as a constructor to initialize an object's state when an instance of a class is created. It is automatically invoked by the Python runtime upon object instantiation, making it a core part of the object-oriented programming model in Python.

Answer

`__bar__`

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`__main__`

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`__foo__`

Question 11

A Python script placed in /opt/myapp/script.py fails with ImportError when run from a cron job with the command: python /opt/myapp/script.py. The script works when run manually from the /opt/myapp/ directory. The script contains the line: from . import config. The config module is located in /opt/myapp/lib/config.py with an __init__.py in /opt/myapp/lib/. What is the most likely cause of the failure?

Accepted Answer

Relative imports are not allowed in a script that is executed directly because its __name__ is not set to a package name.. When a Python script is executed directly (e.g., `python /opt/myapp/script.py`), its `__name__` is set to `'__main__'`, not to a package name. Relative imports (like `from . import config`) require the importing module to be part of a package with a proper `__name__` reflecting the package hierarchy. Since the script is run as the top-level entry point, the relative import fails with an `ImportError`. This explains why the script works when run manually from `/opt/myapp/` (if the working directory is set appropriately, but the relative import still fails unless the script is run as a module with `-m`), but fails from cron where the working directory is typically the user's home directory.

Answer

The __init__.py file in the lib directory is empty and should contain imports.

Answer

The lib directory is not in sys.path when the script is run from cron.

Answer

The cron job uses a different Python interpreter that does not have the required standard library.

Question 12

A team is implementing a shape hierarchy with a base class `Shape` that should have an `area()` method. They want to ensure that every subclass must provide its own implementation of `area()`. Which approach should they use?

Accepted Answer

Use `@abstractmethod` from the `abc` module to declare `area()` as abstract.. The `abc` module provides the `ABCMeta` metaclass and the `@abstractmethod` decorator, which together enforce that any concrete subclass must override the abstract method. If a subclass fails to implement `area()`, Python raises a `TypeError` at instantiation time, ensuring the design contract is upheld. This is the standard Pythonic way to define abstract base classes and enforce method implementation in subclasses.

Answer

Define `area()` in `Shape` and have it raise `NotImplementedError`.

Answer

Use a class method that must be overridden.

Answer

Define `area()` as a property that raises an error.

Question 13

You are a developer for an e-commerce platform. The system receives product descriptions from suppliers in various formats. One supplier sends descriptions with inconsistent capitalization, extra whitespace, and occasional leading/trailing punctuation. Your task is to write a function that normalizes these descriptions: convert to lowercase, remove leading/trailing whitespace and punctuation (.,!?;:), and replace multiple spaces with a single space. The function should return the cleaned string. Which implementation correctly performs all these steps?

Accepted Answer

def normalize(s): import re; s = s.strip(); s = s.strip('.,!?;:'); s = s.lower(); s = re.sub(r'\s+', ' ', s); return s. It performs all required steps in the correct order: it first strips leading/trailing whitespace with `strip()`, then removes leading/trailing punctuation using `strip('.,!?;:')`, converts to lowercase with `lower()`, and finally replaces multiple spaces with a single space using `re.sub(r'\s+', ' ', s)`. This ensures that punctuation is removed only from the edges after whitespace is handled, and internal whitespace is normalized last.

Answer

def normalize(s): return ' '.join(s.lower().split())

Answer

def normalize(s): return s.lower().strip('.,!?;: ')

Answer

def normalize(s): return s.strip().lower()

Question 14

Which THREE are valid ways to create a multiline string in Python?

Accepted Answer

s = ('Line1
' 'Line2'). Options A, B, and C are all valid ways to create a multiline string in Python. Option A uses implicit string concatenation within parentheses; the `
` escape sequence inserts a newline, resulting in a multiline string. Option B uses triple double quotes to span multiple lines physically, preserving line breaks. Option C uses triple single quotes, which work identically to triple double quotes for multiline strings. Option D uses a backslash for line continuation, which does not insert a newline into the string—it just continues the literal on the next line, so the result is a single-line string without a newline. Option E causes a syntax error because a single-quoted string literal cannot span multiple lines without a continuation character.

Answer

s = "Line1\
Line2"

Answer

s = 'Line1
Line2'

Question 15

A developer writes a script to read a configuration file that may not exist. The script should handle the error gracefully and continue. Which approach is most Pythonic?

Accepted Answer

Use a try-except block catching FileNotFoundError. It directly catches the specific `FileNotFoundError` exception, which is a subclass of `OSError` and is raised when a file does not exist. This approach follows the Pythonic principle of EAFP (Easier to Ask for Forgiveness than Permission), allowing the script to attempt the operation and handle the failure gracefully without redundant checks.

Answer

Use a try-except block catching OSError

Answer

Use os.path.exists to check, then open if it exists

Answer

Use an if statement to check file size