How to use Pylint to review code

Code review is importance in the software development process as it serves multiple critical purposes. It helps the programmers to identify and rectify bugs, logical errors, and vulnerabilities before they manifest in the production environment. It is a proactive approach to software development that improves code reliability and enhances the overall quality of the end product. One useful tool for ensuring coding standards and improving code quality is Pylint.

Pylint

Pylint is a popular staticwithout executing the code code analysis tool for Python that helps developers write cleaner, more readable, and more maintainable code. It reviews the code without actually running it and checks for code quality, style, and adherence to coding standards. Pylint is highly extensible and configurable. This includes enabling or disabling specific checks, adjusting issue severity levels, and even crafting custom checks.

Pylint input

Pylint requires the filename of the Python code we wish to review as input. This input is provided using the following command:

[MESSAGES CONTROL] is used to control which types of messages Pylint should enable or disable. These MESSAGES categorize the issues into 6 main categories:

Information (I). Displays informational messages.
Convention (C). Displays when the code does not follow standard conventions.
Warning (W). Displays when the code has Python specific problems.
Refactor (R). Displays when bad code smellAn indication of a deeper problem in the code is present in the code.
Error (E). Displays when bugs are present in the code.
Fatal (F). Displays when errors, preventing Pylint from further processing, are present.

The CONTROL allows us to customize how to handle these message categories. This involves enabling or disabling specific MESSAGES as required.

disable = W0311 disables a specific Pylint warning. Here, W0311 corresponds to the warning about "bad indentation," meaning that Pylint will not report issues related to inconsistent or incorrect indentation in the code.

Code

Here's the coding example to use Pylint to review code.

main.py

config.pylintrc

good_code.py

bad_code.py

import subprocess
# Function to perform code analysis using pylint
def code_analysis(file_path):
    try:
        result = subprocess.run(['pylint', '--rcfile', 'config.pylintrc', file_path], stdout=subprocess.PIPE, stderr=subprocess.PIPE, text=True)
        analysis_result = result.stdout
    
    except Error:
        analysis_result = f"Some error has occurred {Error}"
    return analysis_result
def main():
    
    print("Welcome to the AI-Powered Code Review Assistant!")
    file_path_bad = 'bad_code.py'
    file_path_good = 'good_code.py'
    
    code_bad = open(file_path_bad).readlines()
    code_good = open(file_path_good).readlines()
    
    analysis_result_bad = code_analysis(file_path_bad)
    analysis_result_good = code_analysis(file_path_good)
    analysis_code = code_analysis('wrong_file.py')
    
    
    print("Analysis of bad_Code.py",analysis_result_bad)
    print('Analysis of non_existent file is ',analysis_code)
    print("Analysis of good_code.py",analysis_result_good)
main()

Explanation of main.py

Line 1: Imports the subprocess module to interact with the system's shell or command-line interface from within a Python script.
Lines 4–5: Defines a function code_analysis that takes a file_path as its parameter and uses try/except block for unexpected errors.
Line 6: subprocess.run() function executes the pylint command with provided options and arguments, capturing the standard output and standard error as text and storing the result in the result variable.
Line 8: Assigns the standard output from the result object containing the output of the executed command to the variable analysis_result.
Line 10–11: Raises an exception and prints the error message.
Line 13: Returns the analysis_result.
Line 16–18: Defines a function main and prints a welcome message.
Line 20–21: Assign the names of the Python files that we intend to review to the variables file_path_bad and file_path_good.
Line 23–24: Read the contents of two Python files and storing their contents as lists of lines in the variables code_bad and code_good.
Line 26–28: Calls code_analysis function on three different Python files: file_path_bad, file_path_good, and 'wrong_file.py'.
Line 30–33: Prints the results after analyzing all the files.

Explanation of config.pylintrc

Line 1: Represents the section headers.
Line 2: The msg_id we want to disable. This configuration disables the bad indentation found in our code.

The code we want to review is written in the files bad_code.py and good_code.py.

Pylint output

After analyzing the Python code, Pylint generates the output in the following format:

{file_path}:{line_no}:{column_no}. The specific position within the file during a code analysis process.
{message_id}. The id or code associated with a specific message. The id tells about the category of the message.
{message}. The content of the message. The message text provides detailed information and context about the message.
{symbol}. The symbolic name of the message.

Pylint provides a global evaluation for the code's overall quality, represented on a scale of 0 to 10. A higher score indicates a higher level of the code quality. This score is displayed in all categories except in Fatal message category. The evaluation score is presented for all message categories, with the exception of the Fatal category, which halts Pylint's further processing due to critical errors.

Analysis of bad_code.py ************* Module bad_code
bad_code.py:12:0: C0303: Trailing whitespace (trailing-whitespace)
bad_code.py:1:0: C0114: Missing module docstring (missing-module-docstring)
bad_code.py:1:0: C0103: Module name "bad_code" doesn't conform to snake_case naming style (invalid-name)
bad_code.py:3:4: E0213: Method 'print' should have "self" as first argument (no-self-argument)
bad_code.py:1:0: R0903: Too few public methods (1/2) (too-few-public-methods)
bad_code.py:7:0: C0116: Missing function or method docstring (missing-function-docstring)
bad_code.py:7:0: C0103: Function name "my_Function" doesn't conform to snake_case naming style (invalid-name)
bad_code.py:8:12: E0602: Undefined variable 'i' (undefined-variable)
bad_code.py:9:14: E0602: Undefined variable 'i' (undefined-variable)
bad_code.py:10:0: C0116: Missing function or method docstring (missing-function-docstring)
bad_code.py:10:8: W0613: Unused argument 'fruit_name' (unused-argument)
-----------------------------------
Your code has been rated at 0.00/10

Output of bad_code file after reviewing the code