PCAP Practice Exam 3 — 20 Questions

Question 1

Consider the following code snippet:

try:
    x = int(input())
    y = 10 / x
    print(y)
except ZeroDivisionError:
    print('Division by zero')
except ValueError:
    print('Invalid integer')

If the user enters '0', what is the output?

Accepted Answer

Division by zero. When the user enters '0', the input is successfully converted to the integer 0 by int(), so no ValueError occurs. Then 10 / 0 raises a ZeroDivisionError, which is caught by the except ZeroDivisionError block, printing 'Division by zero'. Option C is correct because the code never reaches the ValueError handler.

Answer

No output

Answer

Both 'Invalid integer' and 'Division by zero'

Answer

Invalid integer

Question 2

Which expression returns the last character of string s?

Accepted Answer

s[-1]. Python uses zero-based indexing for strings, where negative indices count from the end. s[-1] directly accesses the last character of the string, as -1 refers to the final element in the sequence.

Answer

s[len(s)]

Answer

s[-0]

Answer

s[0]

Question 3

Refer to the exhibit. If the file config.cfg exists but the user does not have read permission, what will be printed?

Accepted Answer

'Permission denied'. When `open()` is called on a file that exists but the user lacks read permission, Python raises a `PermissionError`. Since no exception handling is present, the exception is unhandled and Python prints a traceback to stderr which includes the error message `'Permission denied'` (among other details). Option B correctly identifies the permission-denied message that appears in the output.

Answer

An unhandled exception is raised

Answer

Nothing; the program continues silently

Answer

'File not found'

Question 4

Which TWO statements about Python strings are correct? (Choose exactly 2 correct answers.)

Accepted Answer

Strings are immutable; operations like concatenation produce a new string.. Python strings are immutable, meaning once a string object is created, its content cannot be changed. Any operation that appears to modify a string, such as concatenation with the + operator, actually creates a brand-new string object in memory, leaving the original unchanged.

Answer

Strings are mutable; you can change individual characters via indexing.

Answer

Strings have an .append() method to add characters at the end.

Answer

You can assign a new character to a position in a string using indexing: s[0] = 'a'.

Question 5

A programmer writes a function to check if a string is a palindrome (ignoring case and non-alphanumeric characters). Which implementation correctly achieves this?

Accepted Answer

def is_pal(s): s = ''.join(c for c in s if c.isalnum()).lower(); return s == s[::-1]. It first filters the string to keep only alphanumeric characters using `c.isalnum()`, converts the result to lowercase with `.lower()`, and then compares the string to its reverse using slicing `s[::-1]`. This correctly handles case insensitivity and ignores non-alphanumeric characters, which is the standard approach for palindrome checking in Python.

Answer

def is_pal(s): s = s.lower(); return s == ''.join(reversed(s))

Answer

def is_pal(s): return s == s[::-1]

Answer

def is_pal(s): s = s.lower(); return s == s[::-1]

Question 6

What is the result of the expression 'Hello' * 3?

Accepted Answer

'HelloHelloHello'. In Python, the multiplication operator (*) on a string repeats the string a specified number of times. 'Hello' * 3 concatenates 'Hello' three times, producing 'HelloHelloHello'. This is a fundamental string operation defined in Python's sequence protocol.

Answer

'Hello3'

Answer

'Hello Hello Hello'

Answer

TypeError

Question 7

Which of the following statements about class inheritance in Python are true? (Choose two.)

Accepted Answer

Abstract base classes can be defined using the ABC module.. Python's `abc` module (Abstract Base Classes) allows you to define abstract base classes by inheriting from `ABC` and using the `@abstractmethod` decorator. This enforces that subclasses must implement the abstract methods, providing a formal interface contract.

Answer

A class can inherit from only one base class.

Answer

A child class can override any method from its parent class, but only if the method is declared as virtual.

Answer

The super() function is used to call a method from a sibling class.

Question 8

Which TWO statements are true regarding strings in Python?

Accepted Answer

Strings can be concatenated with the + operator.. Strings in Python support concatenation using the + operator, which joins two or more strings into a single string. This is a fundamental operation for combining textual data, and it works by creating a new string object that contains the characters from both operands in sequence.

Answer

Strings are not sequences.

Answer

Strings are mutable.

Answer

Strings do not support indexing.

Question 9

Which TWO of the following are correct ways to raise a custom exception in Python? (Assume CustomError and CustomException are user-defined.)

Accepted Answer

raise CustomError("invalid"). It raises a user-defined exception by instantiating the custom exception class `CustomError` with an argument (the string "invalid"). In Python, the `raise` statement must be followed by an exception instance or an exception class; `CustomError("invalid")` creates an instance of the custom exception, which is the proper way to raise a custom exception with a custom message.

Answer

raise "Custom error"

Answer

raise 42

Answer

raise Exception

Question 10

Which TWO of the following are valid uses for the '__name__' variable in a Python module?

Accepted Answer

To check if the module is being run as the main program.. The '__name__' variable is set to the string '__main__' when the module is executed directly as the main program (e.g., via 'python module.py'). This allows a module to include code that runs only when it is the entry point, not when it is imported by another module. The check is typically done with 'if __name__ == "__main__":'.

Answer

To get the file path of the module.

Answer

To control which names are exported when using 'from module import *'.

Answer

To determine which module imported it.

Question 11

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 12

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 13

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 14

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 15

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 16

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 17

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 18

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 19

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 20

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()