PCAP Practice Test 18 — 15 Questions

Question 1

A developer has a project structure with 'my_package/' containing '__init__.py', 'module_a.py', and 'sub_package/' (with its own '__init__.py'). They want to import function 'foo' from 'module_a' inside a script in 'sub_package' using a relative import. Which statement is correct?

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

Accepted Answer

from ..module_a import foo. The script is inside 'sub_package/', which is one directory level below 'my_package/'. To import from 'module_a' (located in the parent package 'my_package'), a relative import uses '..' to go up one package level, then specifies the module name. Thus, 'from ..module_a import foo' correctly navigates the package hierarchy.

Answer

from .module_a import foo

Answer

from my_package.module_a import foo

Answer

from ..my_package.module_a import foo

Question 2

Consider the following class hierarchy: class A: def method(self): return 'A'; class B(A): pass; class C(A): def method(self): return 'C'; class D(B, C): pass. What is the output of D().method() according to Python's MRO?

Accepted Answer

'C'. Python's MRO (Method Resolution Order) for class D(B, C) is computed using the C3 linearization algorithm, which respects the local precedence order and monotonicity. The MRO for D is D -> B -> C -> A, so D().method() resolves to C.method(), returning 'C'. Option D is correct because C is the first class in the MRO that defines method().

Answer

'B'

Answer

TypeError

Answer

'A'

Question 3

What is the output of the code in the exhibit?

Accepted Answer

Alice is 30 years old.. The code uses an f-string which substitutes the values of the variables `name` and `age` into the string. Evaluating the expression results in 'Alice is 30 years old.', matching option B. Option A shows the literal braces, option C displays the variable names instead of their values, and option D reverses the order of the variables.

Answer

{name} is {age} years old.

Answer

name is age years old.

Answer

30 is Alice years old.

Question 4

A developer is troubleshooting an ImportError: 'No module named 'config''. The config module is located in a subdirectory 'utils' relative to the script. The script's current working directory is the parent of 'utils'. Which of the following lines, added to the script, will resolve the issue?

Accepted Answer

sys.path.append('utils'). The ImportError occurs because Python's module search path (sys.path) does not include the 'utils' subdirectory. Adding 'utils' to sys.path via sys.path.append('utils') tells Python to look inside that directory for modules, resolving the import. Option B is correct because it extends the search path to include the directory containing the config module, without altering the script's working directory or incorrectly appending a file path.

Answer

sys.path.append('utils/config.py')

Answer

sys.path = os.path.join(sys.path, 'utils')

Answer

os.chdir('utils')

Question 5

Which TWO of the following are valid ways to import specific names from a module?

Accepted Answer

from module import name1, name2. The `from module import name1, name2` syntax allows importing specific names from a module directly into the current namespace. Option C is also correct because `from module import name as alias` provides the same functionality while allowing you to rename the imported name to avoid naming conflicts.

Answer

from module import * (only names listed in __all__)

Answer

import name1, name2 from module

Answer

import module.name1

Question 6

What is the cause of the error?

Accepted Answer

The result of `username.encode('utf-8')` is bytes, and Python does not allow concatenating str with bytes.. `username.encode('utf-8')` returns a bytes object, and Python's `+` operator does not allow concatenation of `str` and `bytes` types. This raises a `TypeError: can only concatenate str (not "bytes") to str` because the other operand in the concatenation is a string literal.

Answer

The error is because `encode` returns a string, but the plus operator expects two strings.

Answer

The `username` variable is of type bytes, so encoding is unnecessary.

Answer

The encode method is called incorrectly; it should be `username.encode()` without argument.

Question 7

A developer runs pip install package==1.0 and gets the above error. What is the most likely solution?

Accepted Answer

Use pip install package==2.0 instead.. The error indicates that version 1.0 of the package does not exist in the repository. By specifying a higher version like 2.0 that does exist, pip can successfully download and install the package. This is a common scenario when a package has never released version 1.0 or has skipped it.

Answer

Run pip update to upgrade pip.

Answer

Install from a different repository.

Answer

Check if the package name is correct.

Question 8

A developer is building an IoT application that reads temperature data from a sensor over a TCP socket. The sensor sends data as a stream of bytes encoded in UTF-8, with each reading terminated by a newline character. The developer uses the following code to receive data:

```python
import socket
s = socket.socket()
s.connect(('sensor.local', 5000))
data = s.recv(1024)
```

The variable `data` is a bytes object. The developer needs to convert it to a string to parse the temperature value. Which of the following lines of code should the developer use to correctly obtain the string representation of the received data, assuming the data is valid UTF-8 and may contain non-ASCII characters?

Accepted Answer

data.decode('utf-8'). The `recv()` method returns a bytes object. Since the data is valid UTF-8 and may contain non-ASCII characters, the correct way to convert bytes to a string is by calling `data.decode('utf-8')`. This method interprets the byte sequence according to the UTF-8 encoding and returns a Unicode string.

Answer

data.encode('utf-8')

Answer

bytes(data)

Answer

str(data)

Question 9

A data scientist writes a script to parse a configuration file that contains lines in 'key=value' format. Some lines may have malformed data that cause a ValueError when trying to convert the value to an integer. The requirement is to process all valid lines and skip any that cause a ValueError, but continue processing subsequent lines. The script should log a warning for each skipped line, including the line number. Which implementation correctly fulfills this requirement? (Assume the file is opened with 'with open(...) as f'.)

Accepted Answer

Inside a for loop over f, wrap the parsing in a try-except ValueError block, log the error, and continue.. It uses a try-except ValueError block inside the for loop, which catches the specific exception when converting the value to an integer, logs a warning with the line number, and continues to the next line. This ensures all valid lines are processed while malformed lines are skipped without halting execution, fulfilling the requirement exactly.

Answer

Wrap the entire file processing in a try-except ValueError block; if an error occurs, log and break.

Answer

Before parsing, check if the value string consists of digits using str.isdigit; if not, skip the line.

Answer

Inside a for loop over f, wrap the parsing in a try-except Exception block, log the error, and continue.

Question 10

A class named Counter has a class variable count and an instance method increment. The method is defined as def increment(self): Counter.count += 1. What will be the output after executing the following code? c1 = Counter(); c2 = Counter(); c1.increment(); c2.increment(); print(Counter.count, c1.count, c2.count)

Accepted Answer

2 2 2. The class variable `count` is shared across all instances of the `Counter` class. The `increment` method modifies `Counter.count` directly, so after two calls, `Counter.count` becomes 2. Since `c1.count` and `c2.count` refer to the same class variable (they do not have instance attributes shadowing it), both instances reflect the same value of 2.

Answer

2 1 1

Answer

1 1 1

Answer

0 0 0

Question 11

A developer defines a class 'Car' with an attribute 'wheels = 4'. They create two instances: car1 = Car() and car2 = Car(). Then they set car1.wheels = 3. What is the value of car2.wheels?

Accepted Answer

4. In Python, setting an attribute directly on an instance (car1.wheels = 3) creates an instance attribute that shadows the class attribute for that specific instance only. The class attribute 'wheels = 4' remains unchanged and is still accessible via car2.wheels, which has not been overridden. Therefore, car2.wheels retains the class-level value of 4.

Answer

3

Answer

AttributeError

Answer

None

Question 12

A developer wants to ensure that a class attribute is shared among all instances but cannot be modified from outside the class. Which approach is most appropriate?

Accepted Answer

Define a private class attribute (e.g., __shared) and provide a class method to access it. Defining a private class attribute with name mangling (e.g., `__shared`) prevents direct external modification, and providing a class method (using `@classmethod`) allows read-only access to the attribute. This ensures the attribute is shared among all instances (since it belongs to the class, not instances) while enforcing encapsulation.

Answer

Use a property decorator on a class method

Answer

Define a public class attribute and document it as read-only

Answer

Define an instance attribute inside __init__

Question 13

Refer to the exhibit. A developer runs 'pip install pandas==2.0.0' but gets an error stating that the required version is not available. Which command should be used to list all available versions of pandas?

Accepted Answer

pip index versions pandas. `pip index versions pandas` is the command that queries the Python Package Index (PyPI) for all available versions of the specified package. This command was introduced in pip 21.1 and is the proper way to list version history without attempting to install.

Answer

pip search pandas

Answer

pip show pandas

Answer

pip list --all pandas

Question 14

Refer to the exhibit. What happens when the last line is executed?

Accepted Answer

An AttributeError is raised.. When a class defines `__slots__`, it restricts attribute assignment to only those names listed in `__slots__`. Attempting to assign an attribute not in that list (like `city`) raises an `AttributeError` because the instance has no `__dict__` to store dynamic attributes. The `__init__` method does not override this restriction; it simply initializes the allowed slots.

Answer

The attribute 'city' is added dynamically.

Answer

The __slots__ is ignored because __init__ is defined.

Answer

A syntax error occurs.

Question 15

Refer to the exhibit. Which of the following correctly shows the MRO of class D?

Accepted Answer

[D, B, C, A, object]. Python's Method Resolution Order (MRO) for class D, which inherits from B and C (where B inherits from A and C inherits from A), follows the C3 linearization algorithm. The MRO is computed as D -> B -> C -> A -> object, ensuring that each class appears before its parents and that the order respects the local precedence order of D's bases (B before C).

Answer

[D, A, B, C, object]

Answer

[D, B, A, C, object]

Answer

[D, C, B, A, object]