๐Ÿงน Pylintยถ

Just as you wouldnโ€™t go to a black tie dinner without using a lint roller on your tux or dress before walking into the venue, or, in the old days, going over your suit before that all-important interview, you want your Python code to be clean before you let it out into the world for professionals to see. you want to catch bugs before they bite. This is why you would use a linting tool. Pylint is one of the more popular linting tools. This post tells what it is, how to set it up, and how to get started using it.

The Difference Between What Happens When The Python Interpreter Catches Errors And What Happens When You Run A Linterยถ

When you use the Python interpreter to run a Python program, it may not run your program because it catches errors that Python cannot understand. The kinds of errors that keep your Python file from running are called Syntax errors. Once you remove the syntax errors from your program, the Python interpreter runs it, and it begins to do its processing. If it has errors that prevent it from running correctly, these are called run-time errors.

Linting tools inspect your Python files for both kinds of errors plus coding conventions accepted by the Python community. Using a linting tool makes it easier for both the Python interpreter to run your programs and for anyone who works on projects with you to read your code, since they help you follow agreed upon standards.

How Pylint Helps Furtherยถ

Pylint looks for โ€œcode smells,โ€ any characteristics in the source code of a program that possibly indicate deeper problems. In human interactions, you might look for proper grammar when someone is speaking to you, or you might be looking for deeper meaning indicated by the words they use and their voice inflections.

Pylint Environmentยถ

You can run Pylint from the command line or from an editor, such as PyCharm or Visual Studio Code. It works on Linux, Windows, and Mac. We will concentrate on using it from the command line, since using it from an editor uses its command line options. You can experiment with its configurations and easily see more directly how they affect how it runs.

Installing itยถ

You would want to install Pylint into your default Python environment, since you would want to check all of your Python code with it. Assuming that you have Python installed, from the command line, type:

pip install pylint

To run Pylint, type:

pylint myprogram.py

Where myprogram.py is the Python file you want it to check.

Default optionsยถ

By default, Pylint has all error checks and messages enabled. You can configure it to look for and report on five classes of errors:

  • (C) convention, for programming standard violation

  • (R) refactor, for bad code smell

  • (W) warning, for python specific problems

  • (E) error, for likely bugs in the code

  • (F) fatal, for errors occurred that prevent pylint from doing further Processing.

Further Resourcesยถ

About the Authorยถ

Jim Homme is a former professional musician, father of three, husband, and a 32-year veteran in Information Technology. He loves to read and play chess. He leads a team of accessibility testers at Bender Consulting Services. He is the owner of jimhomme.com, where he writes about Python and related technologies.