How to use the command pylint (with examples)

Pylint is a Python code linter, which means it analyzes Python code for potential errors, coding standards violations, and other issues. It helps developers maintain code quality and adhere to Python best practices.

Use case 1: Show lint errors in a file

Code:

pylint path/to/file.py

Motivation: When working on a Python project, it’s essential to ensure that the code is free of errors and adheres to coding standards. By running pylint on a specific file, you can identify any potential issues and lint errors, allowing you to fix them before the code goes into production.

Explanation:

• pylint: This is the command to run the Pylint program.
• path/to/file.py: Replace this with the actual path to the Python file you want to analyze. Make sure to provide the correct path to the file.

Example output:

************* Module file
path/to/file.py:10:0: C0103: Constant name "my_constant" doesn't conform to UPPER_CASE naming style (invalid-name)
...

In the example output above, Pylint detects a lint error in the file by flagging the constant name “my_constant” as not conforming to the UPPER_CASE naming style.

Use case 2: Lint a file and use a configuration file

Code:

pylint --rcfile path/to/pylintrc path/to/file.py

Motivation: Using a configuration file allows you to customize Pylint’s behavior and enable or disable certain rules. This feature is useful when you want to enforce specific coding standards or ignore certain types of lint errors.

Explanation:

• pylint: The command to run Pylint.
• --rcfile path/to/pylintrc: This argument specifies the path to the configuration file, usually named pylintrc. Modify path/to/pylintrc with the actual path to the configuration file.
• path/to/file.py: Replace this with the actual path to the Python file you want to analyze.

Example output:

************* Module file
path/to/file.py:10:0: C0103: Constant name "my_constant" doesn't conform to UPPER_CASE naming style (invalid-name)
...

The output in this example is similar to the previous use case, but using a configuration file allows you to enable/disable rules and customize Pylint’s behavior further.

Use case 3: Lint a file and disable a specific error code

Code:

pylint --disable C,W,no-error,design path/to/file

Motivation: There might be specific error codes that you want to ignore during the linting process. Disabling these error codes can be useful if you want to exclude certain types of errors or warnings from being reported by Pylint.

Explanation:

• pylint: The command to run Pylint.
• --disable C,W,no-error,design: This argument specifies the error codes that you want to disable. Replace C, W, no-error, design with the actual error codes you want to disable. Multiple error codes can be separated by commas.
• path/to/file: Replace this with the actual path to the Python file you want to analyze.

Example output:

************* Module file

In this example, the output does not show any specific lint errors because the error codes C, W, no-error, and design have been disabled. No linting issues related to those error codes will be reported.

Conclusion:

Pylint is a powerful tool for static code analysis in Python. In this article, we explored three common use cases of the pylint command. We learned how to show lint errors in a file, lint a file using a configuration file, and disable specific error codes during the linting process. By utilizing these use cases, you can maintain code quality, adhere to coding standards, and create more robust and reliable Python applications.