PCPP1 Best Practices And Coding Conventions — 30 Questions

Question 1

Which practice is recommended when dealing with 'bare' except clauses in Python?

Accepted Answer

Always specify the exception type you intend to catch.. Bare 'except:' clauses catch SystemExit and KeyboardInterrupt, which can prevent the user from stopping a program.

Answer

Use bare 'except:' for performance optimization.

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Use 'except Exception:' as the standard catch-all.

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Use 'except:' but log the error immediately.

Question 2

When should you use absolute imports over relative imports in a large project?

Accepted Answer

Always, as they are PEP 8 recommended for clarity and robustness.. Absolute imports are recommended by PEP 8 because they are clearer and avoid ambiguity in complex package structures.

Answer

When the file is in the same directory.

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Only if using Python 2.

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When performance is the main priority.

Question 3

You need to ensure your code is readable by other Python developers. Which naming style should be used for variable names?

Accepted Answer

snake_case.. PEP 8, the official Python style guide, mandates snake_case (all lowercase with underscores) for variable and function names. This convention is universally adopted across the Python standard library and community projects, making code immediately readable to other Python developers. Following PEP 8 ensures consistency and interoperability with tools like linters and formatters.

Answer

UPPER_SNAKE_CASE.

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camelCase.

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PascalCase.

Question 4

Which of the following is the correct way to handle whitespace around an operator according to PEP 8?

Accepted Answer

x = y + z. PEP 8 specifies that binary operators should be surrounded by exactly one space on each side when used in assignment or arithmetic expressions, so 'x = y + z' is the canonical form. This improves readability and is enforced by linters like flake8 and pycodestyle (E225, E226). The other options either omit spaces entirely or use multiple spaces, both of which violate the style guide.

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x= y +z

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x  =  y  +  z

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x=y+z

Question 5

Which THREE elements are essential for a good Python docstring?

Accepted Answer

A detailed description of the logic.. Option A is correct because a good docstring should include a detailed description of the logic, explaining how the object works beyond just its purpose. Option C is correct because a docstring must begin with a brief summary of the object's purpose, giving readers a quick understanding of what the function, class, or module does. Option D is correct because PEP 257 recommends a blank line after the summary line before any further elaboration, separating the one-line summary from the detailed description. Option B is not essential since docstrings describe behavior and usage, not an exhaustive list of variable types, which belongs in type hints or annotations. Option E is not appropriate because a docstring should not duplicate the full source code, which is already visible in the implementation.

Answer

A list of all possible variable types in the code.

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The full source code of the function.

Question 6

You are writing a Python module that includes a function named `calculate_metrics`. The function accepts a required integer parameter `count`, an optional float parameter `threshold` with a default value, and an arbitrary number of additional keyword arguments. You want to add a docstring that follows the Google Python Style Guide. Which of the following is the correct way to document the parameters?

Accepted Answer

Args:
    count (int): The number of items to process.
    threshold (float, optional): The cutoff value. Defaults to 0.5.
    **kwargs: Additional keyword arguments.. The Google Python Style Guide specifies that function docstrings should include an 'Args:' section. Each parameter is listed with its name, type in parentheses, and a description. Optional parameters are indicated with ', optional' and their default value. Arbitrary keyword arguments (**kwargs) are listed without a type. The other options use different docstring conventions (NumPy, reST) or incorrectly type **kwargs.

Answer

Args:
    count (int): The number of items to process.
    threshold (float, optional): The cutoff value. Defaults to 0.5.
    kwargs (dict): Additional keyword arguments.

Answer

Parameters:
    count: int
        The number of items to process.
    threshold: float, optional
        The cutoff value. Defaults to 0.5.
    kwargs: dict
        Additional keyword arguments.

Answer

:param count: The number of items to process.
:type count: int
:param threshold: The cutoff value. Defaults to 0.5.
:type threshold: float, optional
:param kwargs: Additional keyword arguments.
:type kwargs: dict

Question 7

A development team is configuring a continuous integration pipeline for a Python package. They want to enforce PEP 8 style rules automatically. Which combination of tools should they integrate into the pipeline to check style and automatically fix common issues?

Accepted Answer

flake8 and black. flake8 and black are standard tools for PEP 8 enforcement. flake8 checks style and reports violations, while black automatically reformats code to a consistent style. This pairing allows CI pipelines to both detect and fix style issues, ensuring code adheres to PEP 8 with minimal manual intervention.

Answer

mypy and isort

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pycodestyle and yapf

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pylint and autopep8

Question 8

A team is reviewing Python code for compliance with PEP 8's recommendations on comments. Which two of the following practices are correct according to PEP 8? (Choose two.)

Accepted Answer

Block comments should be indented to the same level as the code they describe.. PEP 8 recommends that comments be complete sentences with proper capitalization, and that block comments be indented to match the code they describe. Inline comments should be separated by at least two spaces, but that option was not selected as correct because the stem asks for two practices and the other correct options are more directly about comment content and placement.

Answer

Inline comments should be separated from the code by at least two spaces.

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Comments should be written in English, unless coding for a non-English speaking audience.

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Comments should be used to explain complex code, but also to disable code temporarily.

Question 9

A Python developer is reviewing a pull request and notices that a function is defined as `def calculate_total(items):` but the function returns a value that is never used. According to PEP 8, what is the recommended way to indicate that the return value is intentionally ignored?

Accepted Answer

Call the function without assigning its return value, and add a comment explaining why.. PEP 8 emphasizes code readability and explicitness. When a function's return value is not needed, simply calling the function without assignment is acceptable, especially if the function is invoked for its side effects. Adding a comment to explain why the return value is ignored improves clarity for future maintainers. This practice avoids unnecessary variable assignments and aligns with Python's philosophy of simplicity.

Answer

Prefix the function call with `# noqa` to suppress linter warnings.

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Use the `del` statement on the return value immediately after the call.

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Assign the return value to a variable named `_`.

Question 10

A developer is writing a context manager class to manage a database connection. They want to ensure that the connection is properly closed even if an exception occurs within the with block. Which method implementation correctly follows the context manager protocol?

Accepted Answer

__enter__ returns self and __exit__ closes the connection, returning False.. A context manager's __exit__ should release resources and return False to allow exceptions to propagate. Returning True suppresses exceptions, which is rarely desired. Not closing the resource or raising a new exception in __exit__ can mask errors or cause leaks. The correct implementation closes the connection and returns False.

Answer

__enter__ returns self and __exit__ closes the connection, returning True.

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__enter__ returns the connection and __exit__ does not close it, returning False.

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__enter__ returns the connection and __exit__ closes it, but raises an exception if any occurred.

Question 11

A developer is writing a Python module that includes a function `calculate_statistics(data)`. They want to provide comprehensive documentation that can be automatically extracted by tools like Sphinx. Which docstring style should they use to ensure proper rendering of parameters, return values, and exceptions?

Accepted Answer

reStructuredText (reST) with field lists. reStructuredText with field lists is the standard for Sphinx documentation. It allows Sphinx to parse and render parameters, return values, and exceptions without additional extensions. While Google and NumPy styles are popular, they require the napoleon extension to work with Sphinx, adding complexity.

Answer

Google style docstrings

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Plain text docstrings without special formatting

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NumPy style docstrings

Question 12

A team is preparing a Python package for release and wants to follow PEP 8 conventions for whitespace and naming. Which two practices are correct according to PEP 8? (Choose two.)

Accepted Answer

Surround top-level function and class definitions with two blank lines.. PEP 8 calls for two blank lines around top-level definitions and CapWords for class names. These two rules shape the visual structure of a module and the naming of its types, making them foundational for a package release. Other listed practices either misstate the whitespace rules for annotated defaults or introduce spacing that the guide discourages.

Answer

Use a single space on both sides of the `=` sign when assigning a default value to a function parameter that also has a type annotation.

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Place a space before the opening parenthesis when calling a function, as in `process (data)`.

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Separate method definitions inside a class with a single blank line.

Question 13

A developer is writing a Python module and wants to follow PEP 8 naming conventions for classes, functions, variables, and constants. Which TWO of the following naming styles are correct according to PEP 8? (Choose two.)

Accepted Answer

function_name for functions. PEP 8 specifies CapWords for class names and lowercase_with_underscores for function names. These conventions improve readability and consistency. Other styles like camelCase for variables or uppercase for locals are not recommended, as they deviate from standard Python practices.

Answer

UPPERCASE for local variables

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camelCase for global variables

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CONSTANT_NAME for constants

Question 14

You are reviewing a Python module that defines a function to calculate the area of a circle. The function is part of a public API and should be documented using a docstring. Which of the following is the most appropriate docstring for this function according to PEP 257?

Accepted Answer

"""Calculate the area of a circle.

Args:
    radius (float): The radius of the circle.

Returns:
    float: The area of the circle.
""". A good docstring should start with a concise one-line summary ending with a period, followed by a blank line and then detailed sections. The Google style shown in the correct option provides clear, structured documentation for parameters and return values, making the API self-documenting and tool-friendly. This aligns with PEP 257 recommendations for multi-line docstrings and common community conventions.

Answer

"""This function calculates the area of a circle given its radius. It uses the formula pi * r^2. The radius must be a positive number."""

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"""Calculate area.

:param radius: The radius.
:return: The area.
"""

Answer

"""area(radius) -> float
Computes area.
"""

Question 15

A developer is reviewing a Python module for compliance with PEP 8's naming conventions. Which two of the following naming practices are correct according to PEP 8? (Choose two.)

Accepted Answer

Using lowercase with underscores for function names, such as calculate_average.. PEP 8 prescribes snake_case for functions and variables, and CapWords (CamelCase) for classes. Constants should be uppercase with underscores. Using these conventions consistently makes Python code more readable and maintainable. The two correct practices are using lowercase with underscores for function names and CamelCase for class names, as they align with the standard naming conventions for their respective scopes.

Answer

Using uppercase with underscores for local variable names, such as MAX_RETRIES.

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Using single leading underscores for public method names, such as _get_data.

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Using mixedCase for module-level variables, such as maxRetries.

Question 16

A developer is writing a Python function that takes several parameters. They want to follow PEP 8 recommendations for breaking long lines. Which of the following is the preferred way to align arguments when a function call spans multiple lines?

Accepted Answer

Align the arguments vertically under the first argument, using opening delimiter alignment.. PEP 8 recommends using opening delimiter alignment for function calls that span multiple lines: the first argument goes on the same line as the opening parenthesis, and subsequent arguments align vertically under it. This style is clear and consistent. Alternatively, a hanging indent can be used, but it must be distinguishable from the block indentation. The key is to avoid backslashes and ensure readability.

Answer

Place each argument on a new line, indented by exactly 8 spaces from the start of the line.

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Use a hanging indent with a fixed number of spaces (e.g., 4) for all continuation lines.

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Use backslashes to continue the line and align arguments under the first argument.

Question 17

According to PEP 257, what is the standard format for a single-line docstring?

Accepted Answer

Use triple quotes and keep the summary on the same line, ending with a period.. A single-line docstring should be on the same line as the opening triple quotes, ending with a period.

Answer

Use a single quote for the entire block.

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The docstring should span three lines including the summary.

Answer

The summary should start on the next line.

Question 18

When naming a constant in Python, which convention does PEP 8 recommend?

Accepted Answer

UPPER_CASE_WITH_UNDERSCORES.. Constants should be named using all capital letters with underscores to separate words.

Answer

PascalCase.

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snake_case.

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CamelCase.

Question 19

You are debugging a legacy application and need to ensure that resources like file handles are always closed. Which construct is preferred?

Accepted Answer

Use a context manager with the 'with' statement.. The 'with' statement invokes a context manager, which guarantees that the __exit__ method runs and closes the file handle even if an exception occurs inside the block. This is the idiomatic, preferred Python construct for deterministic resource cleanup. It is cleaner and safer than manual try/finally code.

Answer

Wrap the file operation in a try-except block.

Answer

Manually call file.close() in a finally block.

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Rely on the garbage collector to close the handle.

Question 20

You are writing a library that expects a custom exception. Which practice aligns best with Python's exception handling hierarchy?

Accepted Answer

Inherit from Exception.. Custom application exceptions should inherit from Exception, which is the base class for all non-system-exiting exceptions and is intended for user-defined errors. Inheriting from Exception ensures the exception is caught by normal 'except Exception' handlers and does not interfere with interpreter-level control flow. This is the standard practice recommended by PEP 8 and the Python documentation.

Answer

Use a mixin class without inheritance.

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Inherit from StandardError.

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Inherit from BaseException.