PCAP Practice Test 10 — 10 Questions

Question 1

Drag and drop the steps to perform unit testing with the unittest framework in Python into the correct order.

Accepted Answer

Import unittest, then create a TestCase subclass, then define test methods (starting with 'test_'), then call unittest.main(). Unit testing with unittest requires importing, creating a TestCase subclass, writing test methods, and calling unittest.main().

Answer

Create a TestCase subclass, then import unittest, then define test methods, then call unittest.main()

Answer

Import unittest, then define test methods, then create a TestCase subclass, then call unittest.main()

Answer

Import unittest, then create a TestCase subclass, then call unittest.main(), then define test methods

Question 2

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.

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The current working directory is not in sys.path.

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The script is running from an interactive shell.

Question 3

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]'

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

Answer

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

Question 4

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.

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Name mangling prevents external code from accessing the attribute entirely.

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Name mangling occurs at runtime.

Question 5

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]

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s[2:5:1]

Question 6

Refer to the exhibit. What is the effect of using 'from None' in the raise statement?

Accepted Answer

It suppresses the exception chain and only shows the TypeError. Using 'from None' suppresses the chaining of exceptions, so the original ValueError is not shown in the traceback.

Answer

It re-raises the original ValueError

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It causes a syntax error

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It chains the TypeError to the original ValueError

Question 7

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.

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

Question 8

Which THREE of the following are true about method overriding in Python?

Accepted Answer

The subclass method must have the same name.. Method overriding in Python requires the subclass method to have the same name as the parent class method. This is the fundamental rule of overriding — without the same name, the method is not overriding but rather defining a new method. The subclass method replaces the inherited method when called on an instance of the subclass.

Answer

The `@override` decorator is required.

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The subclass method can have a different number of parameters.

Question 9

Refer to the exhibit. Which statement about the output is true?

Accepted Answer

a.__class__.__bases__ returns (,). `a.__class__` returns the class of instance `a`, which is `A`. Since `A` does not explicitly inherit from any class, it implicitly inherits from `object`. Therefore, `A.__bases__` returns `(,)`, which is exactly what `a.__class__.__bases__` evaluates to.

Answer

a.__class__.__bases__ returns an empty tuple

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type(a).__bases__ returns (<class 'object'>,)

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Both print statements output the same thing

Question 10

Which of these is NOT a characteristic of Python's descriptor protocol?

Accepted Answer

Descriptors are only used for attributes that are read-only. Descriptors are not limited to read-only attributes; they can control get, set, and delete operations. A descriptor that only implements `__get__` is a non-data descriptor, which can be overridden by instance attributes, while a data descriptor implements both `__get__` and `__set__` (and optionally `__delete__`), allowing full read-write control. The statement that descriptors are only for read-only attributes is false, as they are commonly used for computed properties, validation, and lazy evaluation.

Answer

A descriptor can be used to create properties with custom behavior

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Class variables assigned to a descriptor are automatically intercepted

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A descriptor must implement __get__