PCAP Practice Test 10 — 10 Questions

Question 1

A Python package 'mypackage' contains the following hierarchy:

mypackage/
    __init__.py
    subpackage1/
        __init__.py
        module_a.py
    subpackage2/
        __init__.py
        module_b.py

From a script outside the package, a programmer writes:

import mypackage.subpackage1.module_a

Which statement is true about the import?

Accepted Answer

Both mypackage/__init__.py and mypackage/subpackage1/__init__.py are executed.. When Python encounters an import statement with a dotted path like `import mypackage.subpackage1.module_a`, it executes the `__init__.py` files for each package in the path in order: first `mypackage/__init__.py`, then `mypackage/subpackage1/__init__.py`. This is because Python must initialize each package before it can access its subpackages or modules. Option D correctly states that both `__init__.py` files are executed.

Answer

Only mypackage/__init__.py is executed.

Answer

No __init__.py files are executed because the import uses a dotted path.

Answer

After the import, 'mypackage' is not available as a name in the namespace.

Question 2

A developer wants to check if a string ends with a specific suffix. Which method should be used?

Accepted Answer

endswith(). The `endswith()` method is specifically designed to check if a string ends with a given suffix, returning a boolean value. This is the correct and most direct approach for the task described, as it avoids manual slicing or comparison.

Answer

index()

Answer

find()

Answer

startswith()

Question 3

A Python class 'Shape' defines an abstract method 'area'. Subclasses 'Circle' and 'Square' implement 'area'. A function 'calculate_area(shape)' expects a 'Shape' instance. Which principle ensures that the function works correctly without knowing the specific subclass?

Accepted Answer

Liskov Substitution Principle. The Liskov Substitution Principle (LSP) states that objects of a superclass should be replaceable with objects of its subclasses without affecting the correctness of the program. In this scenario, 'calculate_area(shape)' accepts a 'Shape' instance, and because both 'Circle' and 'Square' are proper subtypes that honor the contract of the 'area' method, the function works correctly regardless of which subclass is passed. This is the core of LSP: substitutability without side effects.

Answer

Interface Segregation Principle

Answer

Single Responsibility Principle

Answer

Dependency Inversion Principle

Question 4

A developer writes a function that reads a file and processes its content. The function should handle the case where the file does not exist without catching other I/O errors. Which exception should be caught?

Accepted Answer

FileNotFoundError. `FileNotFoundError` is a specific subclass of `OSError` that is raised exactly when a file or directory is requested but does not exist. By catching only `FileNotFoundError`, the function handles the missing-file scenario without masking other I/O errors such as permission issues or disk failures, which is the precise requirement stated in the question.

Answer

PermissionError

Answer

IOError

Answer

OSError

Question 5

A log processing script receives a multiline string log. The script needs to check if the string ends with the substring 'ERROR'. Which method should be used?

Accepted Answer

log.endswith('ERROR'). The `endswith()` method is specifically designed to check if a string ends with a given substring. It returns `True` if the string ends with 'ERROR', making it the most direct and readable solution for this requirement.

Answer

log.find('ERROR') != -1

Answer

log.rfind('ERROR') == len(log)-5

Answer

'ERROR' in log

Question 6

You are a developer at a company that processes customer feedback. Each feedback entry is stored as a string containing a rating (1-5) followed by a colon and then the comment. For example: '4: Great service'. You need to extract only the comments from feedback that have a rating of 4 or 5. You have a list of feedback strings. Which code snippet correctly implements this?

Accepted Answer

[s.split(':')[1].strip() for s in feedback if s.split(':')[0].strip() in ('4','5')]. It splits each feedback string on ':', extracts the comment (index [1]), strips whitespace, and filters only those entries where the rating (index [0], stripped) is exactly '4' or '5'. This ensures only comments from high-rated feedback are collected, handling potential spaces around the colon.

Answer

[s for s in feedback if s.startswith('4') or s.startswith('5')]

Answer

[s.split(':') for s in feedback][1]

Answer

[s.split(':')[1] for s in feedback if '4' in s or '5' in s]

Question 7

A Python developer is implementing a class that should behave like a sequence and support indexing. Which pair of special methods must be defined to achieve this?

Accepted Answer

__getitem__ and __len__. To make a class behave like a sequence and support indexing (e.g., obj[0]), Python requires the __getitem__ method to retrieve items by key. Additionally, the __len__ method is needed to define the length of the sequence, which is used by built-in functions like len() and is part of the sequence protocol. Together, these two methods satisfy the minimal requirements for a sequence-like object that supports indexing.

Answer

__getitem__ and __contains__

Answer

__setitem__ and __delitem__

Answer

__iter__ and __next__

Question 8

A data pipeline processes CSV lines that may contain quoted fields with commas inside double quotes. For example: 'John, "Doe, Jr.", 35'. The team needs to split such a line correctly. Which approach is best?

Accepted Answer

Use csv.reader([line]) to parse the line.. Python's `csv.reader` is specifically designed to handle CSV parsing according to RFC 4180, including quoted fields that contain commas, newlines, and embedded quotes. It automatically manages quote state and field boundaries, making it the most robust and Pythonic solution for this task.

Answer

Manually iterate over characters and track quote state.

Answer

Use str.split(',') after removing all quotes.

Answer

Use re.split(r',(?=(?:[^"]*"[^"]*")*[^"]*$)', line)

Question 9

Consider the following code:

print('"age": 30,')

Accepted Answer

"age": 30,. The code prints a literal string: "age": 30,. The double quotes are escaped within the single-quoted string, so they appear in the output. The trailing comma is part of the string, not a delimiter.

Answer

"age": 30

Answer

"name": "Alice",

Answer

"city": "New York"

Question 10

Which of the following is a valid way to import a module named 'math' and assign it an alias 'm'?

Accepted Answer

import math as m. Python's `import` statement allows you to import a module and assign it an alias using the `as` keyword, as in `import math as m`. This creates a reference to the `math` module under the name `m`, so you can call functions like `m.sqrt(16)` without polluting the namespace with the original module name.

Answer

alias math as m

Answer

from math import * as m

Answer

import m from math