5 Best Ways to Check Python Code Against Programming Conventions

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💡 Problem Formulation: Ensuring that Python code adheres to standard programming conventions is crucial for readability and maintainability. The input to be evaluated includes variable names, function names, indentation levels, and overall code structure. The desired output is a confirmation of adherence to the conventions or a report of any inconsistencies.

Method 1: Using PEP 8 Standards with pep8 Library

PEP 8 is the authoritative style guide for Python code. Using the pep8 library, we can programmatically check if Python code conforms to these conventions. This method checks the code’s syntax, naming conventions, and layout against the PEP 8 guidelines and provides a list of areas that do not conform.

Here’s an example:

import pep8

checker = pep8.Checker('example.py')
report = checker.check_all()
print(report)

Output:

2

In this code snippet, we use the pep8 library to create a checker for a Python file named ‘example.py’. After we run check_all(), the output is the total number of issues found concerning PEP 8 conventions.

Method 2: Using pylint

pylint is a comprehensive tool that checks for errors in Python code, enforces a coding standard, looks for code smells, and offers simple refactoring suggestions. It covers more than just style adherence, providing a global analysis of the code for potential improvements.

Here’s an example:

!pip install pylint
!pylint example.py

Output:

************* Module example
C: 1, 0: Missing module docstring (missing-docstring)
...

This snippet shows how to use the pylint tool from the command line to analyze the ‘example.py’ file. pylint provides detailed feedback about various code issues, including coding standards and structure. The output snippet shows a missing module docstring warning.

Method 3: Using flake8

flake8 is a tool that combines PyFlakes, pycodestyle (formerly pep8), and Ned Batchelder’s McCabe script. It’s a great tool to check your code base against coding style (PEP 8), and programming errors like “library imported but unused” and “undefined name”.

Here’s an example:

!pip install flake8
!flake8 example.py

Output:

example.py:1:1: F401 'os' imported but unused

In the given example, flake8 is run against ‘example.py’ to check for issues. The output indicates an imported library (`os`) is not being used anywhere in the code.

Method 4: Using black for Code Formatting

black is an uncompromising Python code formatter. By reformatting the Python code to a consistent style, it makes it easier to check code against convention arrangements. It may not check the code logic, but it is perfect for ensuring consistent formatting.

Here’s an example:

!pip install black
!black --check example.py

Output:

example.py already well formatted, good job.

This code snippet demonstrates how to use the black tool to check if ‘example.py’ is already formatted according to the strict standards that black enforces. If not, it will format it automatically.

Bonus One-Liner Method 5: Quickly Checking a Python File with Regular Expressions

If you have simple convention checks like checking for underscored variable names or simple block indentation, Python’s re module with regular expressions can be handy, though it’s not as comprehensive as other methods.

Here’s an example:

import re

with open('example.py', 'r') as file:
    file_content = file.read()
    
# Pattern for underscored variable names
pattern = re.compile(r'\b[a-z]+_[a-z]+\b')
matches = pattern.findall(file_content)
print(matches)

Output:

['variable_name', 'another_variable']

This code uses Python’s built-in re module to search for variable names that follow the lowercase with underscores pattern. The findall method returns all occurrences that match this pattern in ‘example.py’.

Summary/Discussion

  • Method 1: pep8 library. Strict adherence to PEP 8. May not cover all potential issues. Easiest for PEP 8 standards.
  • Method 2: pylint. Broad spectrum analysis. Offers refactoring hints. Might be overwhelming due to extensive checks.
  • Method 3: flake8. Combines multiple checks into one tool. Quick and easy to use. Less detailed than pylint.
  • Method 4: black. Enforces strict formatting. Not for logic or naming conventions. Best suited for automatic reformatting.
  • Bonus Method 5: Regular Expressions. Good for simple checks. Not comprehensive. Best for custom patterns.