PCAP Practice Test 12 — 15 Questions

Question 1

A script runs: import sys; print(sys.path[0]). The output is an empty string. What does this indicate?

Accepted Answer

The script is being read from stdin.. When a script is read from stdin (e.g., via `python < script.py` or `echo 'print(1)' | python`), Python sets `sys.path[0]` to an empty string because there is no script file path to derive the directory from. This is the documented behavior: `sys.path[0]` is the directory containing the script, or an empty string if the script is read from standard input.

Answer

Python was launched with the -I flag.

Answer

The current working directory is not in sys.path.

Answer

The script is running from an interactive shell.

Question 2

A QA engineer needs to verify that a user input string contains at least one uppercase letter, one lowercase letter, and one digit. Which regex pattern can be used with re.search() to achieve this?

Accepted Answer

r'(?=.*[A-Z])(?=.*[a-z])(?=.*\d)'. It uses lookahead assertions ((?=...)) to check for the presence of at least one uppercase letter, one lowercase letter, and one digit anywhere in the string, without consuming characters. This allows re.search() to return a match if all three conditions are met, regardless of order.

Answer

r'[A-Za-z0-9]'

Answer

r'([A-Z].*[a-z].*\d)|([a-z].*[A-Z].*\d)|...'

Answer

r'\d.*[a-z].*[A-Z]'

Question 3

Which TWO statements about Python's name mangling are correct?

Accepted Answer

The mangled name format is _ClassName__attribute.. Python's name mangling transforms an attribute name like `__attribute` defined in a class `MyClass` into `_MyClass__attribute`. This mechanism is specifically designed to avoid name clashes in subclasses, not to enforce privacy. The transformation is done by the compiler at definition time, not at runtime.

Answer

Name mangling applies to all method names that start with a single underscore.

Answer

Name mangling prevents external code from accessing the attribute entirely.

Answer

Name mangling occurs at runtime.

Question 4

Given s = 'a1b2c3', which TWO of the following expressions return the string '123'?

Accepted Answer

s[1::2]. Slicing with `s[1::2]` starts at index 1 (the character '1'), goes to the end of the string, and takes every second character, resulting in '1', '2', '3' concatenated as '123'. Option C is also correct because `s[1:6:2]` starts at index 1, stops before index 6 (the string length is 6, so index 6 is just past the last character), and steps by 2, yielding the same sequence of characters.

Answer

s[0:5:2]

Answer

s[0::2]

Answer

s[2:5:1]

Question 5

Match each exception to its cause.

Accepted Answer

ValueError: Raised when a built-in operation or function receives an argument that has the right type but an inappropriate value.. Correct matches: ValueError with inappropriate value, TypeError with wrong type, IndexError with out-of-range index, KeyError with missing key. Common confusions arise from swapping the definitions of ValueError and TypeError, or TypeError and KeyError.

Answer

ValueError: Raised when an operation or function is applied to an object of inappropriate type.

Answer

TypeError: Raised when a mapping key is not found in the set of existing keys.

Question 6

A junior developer is parsing a log file where each line has comma-separated fields. However, some fields are enclosed in double quotes and contain commas inside, e.g., '2023-08-15 14:30:00,WARNING,"Disk space low, please clean up".'. They are required to parse these lines using only built-in string methods (no modules like csv or re). Which approach is the most reliable and efficient?

Accepted Answer

Write a custom parser that iterates over characters, toggles a quote flag, and splits on commas when outside quotes. A custom parser that toggles a quote flag while iterating over characters can reliably distinguish commas inside double quotes from field-separating commas. This approach handles embedded commas and escaped quotes without relying on external modules, making it both efficient and robust for the given constraints.

Answer

Remove all double quotes from the line before splitting

Answer

Use a regular expression that matches commas outside double quotes

Answer

Use the split() method and then merge fields that start with a double quote

Question 7

A class `ServerConfig` has a class attribute `port = 8080`. After deployment, a developer runs `ServerConfig.port = 9090` in one module, and unexpectedly all existing instances now use port 9090. What concept explains this behavior?

Accepted Answer

Class attributes are shared among all instances of a class.. Class attributes in Python are shared across all instances of a class. When you modify `ServerConfig.port` on the class itself, every instance that accesses `port` via the class (or via an instance that hasn't overridden it) sees the new value. This is fundamental to Python's attribute lookup mechanism: instance attributes shadow class attributes, but if no instance attribute exists, the class attribute is used.

Answer

Instance attributes always override class attributes.

Answer

The attribute is immutable.

Answer

Python uses copy-on-write for attribute access.

Question 8

Which of the following correctly uses an abstract base class to enforce that all subclasses implement a 'make_sound' method? (Assume ABC imported)

Accepted Answer

from abc import ABC, abstractmethod
class Animal(ABC):
    @abstractmethod
    def make_sound(self):
        pass. It imports both `ABC` and `abstractmethod` from the `abc` module, defines `Animal` as a subclass of `ABC`, and decorates `make_sound` with `@abstractmethod`. This combination prevents instantiation of `Animal` and forces any concrete subclass to override `make_sound`, or else a `TypeError` is raised at instantiation time.

Answer

from abc import abstractmethod
class Animal:
    @abstractmethod
    def make_sound(self):
        pass

Answer

class Animal:
    def make_sound(self):
        return None

Answer

class Animal:
    def make_sound(self):
        raise NotImplementedError

Question 9

Which THREE of the following are valid string methods in Python? (Choose three.)

Accepted Answer

.capitalize(). All three options A, B, and E are valid Python string methods. .capitalize() returns a copy of the string with its first character capitalized and the rest lowercased. .lower() returns a copy of the string with all characters converted to lowercase. .swapcase() returns a copy of the string with uppercase characters converted to lowercase and vice versa. Options C and D are incorrect because .uppercase() and .titlecase() are not valid Python string methods; the correct methods are .upper() and .title(). Although the question asks to choose two, note that .swapcase() is also a valid method, making three correct options. In such cases, any two of the three valid methods would be acceptable, but the intended correct answers are A, B, and E.

Answer

.uppercase()

Answer

.titlecase()

Question 10

A Python script imports the module 'my_module'. The developer wants to ensure that when the script is run directly, it executes a specific function, but when imported as a module, that function is not executed. Which code snippet achieves this?

Accepted Answer

if __name__ == '__main__': run(). Both options A and B are correct because they are identical and represent the standard Python idiom `if __name__ == '__main__': run()`. When the script is run directly, Python sets `__name__` to `'__main__'`, triggering the function. When imported, `__name__` is the module name, so the function is not executed. Options C and D are incorrect: C relies on an environment variable that is not standard, and D checks `sys.argv[0]` which is the script path, not the module name.

Answer

if os.environ.get('RUN_MAIN'): run()

Answer

if sys.argv[0] == 'my_module': run()

Question 11

Refer to the exhibit. Which of the following fixes the error?

Accepted Answer

Both A and B. Both A and B produce the string 'Hello5' without error. In Python, the + operator concatenates strings, so 'Hello' + '5' works. Option B converts the integer 5 to a string using str() before concatenation, which also works. Option D uses the * operator to repeat the string 'Hello' five times, producing 'HelloHelloHelloHelloHello', which is a valid operation but does not fix the error described in the exhibit (likely a TypeError from trying to concatenate a string and an integer).

Answer

print('Hello' + '5')

Answer

print('Hello' + str(5))

Answer

print('Hello' * 5)

Question 12

Given: class A: def method(self): print('A'); class B(A): def method(self): super().method(); print('B'); class C(A): def method(self): super().method(); print('C'); class D(B, C): pass. What is printed by D().method()?

Accepted Answer

A C B. Python's MRO (Method Resolution Order) for class D, which inherits from B and C (both inheriting from A), follows the C3 linearization algorithm. The MRO for D is D -> B -> C -> A, so calling D().method() triggers B.method(), which calls super().method() (resolving to C.method()), which calls super().method() (resolving to A.method()), printing 'A', then back to C prints 'C', then back to B prints 'B', resulting in 'A C B'.

Answer

A B C

Answer

C A B

Answer

B A C

Question 13

Which TWO of the following are valid ways to define a class method in Python? (Select exactly two.)

Accepted Answer

def my_method(cls): pass
my_method = classmethod(my_method). It manually applies the `classmethod()` built-in function to a regular function, converting it into a class method. This is a valid, though less common, way to define a class method, as the `classmethod` descriptor wraps the function so that the first argument passed is the class (`cls`), not an instance.

Answer

class MyClass:
    def my_method(cls): pass

Answer

def my_method(self): pass

Answer

@staticmethod
def my_method(cls): pass

Question 14

Drag and drop the steps to handle an exception in Python using try-except-finally into the correct order.

Accepted Answer

try block, then except block(s), then else block, then finally block. Exception handling follows the order: try block, except blocks, else block, finally block. The raise statement can be used anywhere to trigger an exception.

Answer

try block, then except block(s), then finally block, then else block

Answer

try block, then else block, then except block(s), then finally block

Answer

else block, then try block, then except block(s), then finally block

Question 15

Which TWO of the following are valid ways to import a function named 'func' from a module 'mymod' that is in the same directory as the script?

Accepted Answer

from mymod import func as myfunc. The syntax `from mymod import func as myfunc` is a valid Python import statement that imports the function `func` from the module `mymod` and binds it to the local name `myfunc`. Since `mymod` is in the same directory as the script, Python's module search path includes that directory, so the import succeeds without needing a relative import prefix.

Answer

import mymod.func

Answer

import func from mymod

Answer

from .mymod import func