Pylint Static Code Analysis | Python Script with Adjustable Score Threshold

Sheep make wool which makes lint and thats about as creative I can get for this article on code lint.

Pylint is an incredibly useful tool for static code analysis. It provides a simple score out of 10, a detailed output on what to fix, and the ability to ignore things you do not believe in.

Pylint - code analysis for Python | www.pylint.org

This is part two of three of a series I am doing on how I use Pylint in my projects.

• Part 1: Executing with Command Line vs Programmatically

Pylint Static Code Analysis | Executing with Command Line vs Programmatically

• Part 2: Pylint Runner Script with Changeable Threshold
• Part 3: A Github Action for Failing Builds under a Pylint Threshold

Pylint Static Code Analysis | Github Action to fail below a score threshold

Python Script with Adjustable Threshold

In the previous article from part 1 above I did a very basic introduction to how to run Pylint programmatically with python. Here I use that same code and more to do the following.

• Parametrize code path input
• Parametrize pylint score threshold
• Run pylint on that input directory
• Fail and exit 1 if the code fails to meet the threshold
• Pass and exit 0 if the code meets the given threshold

I have created this file in my project root as lint.py.

lint.py

First, we read in our two arguements with argarse…

import argparse

parser = argparse.ArgumentParser(prog="LINT")

parser.add_argument('-p',
                    '--path',
                    help='path to directory you want to run pylint | '
                         'Default: %(default)s | '
                         'Type: %(type)s ',
                    default='./src',
                    type=str)

parser.add_argument('-t',
                    '--threshold',
                    help='score threshold to fail pylint runner | '
                         'Default: %(default)s | '
                         'Type: %(type)s ',
                    default=7,
                    type=float)

args = parser.parse_args()
path = str(args.path)
threshold = float(args.threshold)

Next, we run Pylint…

from pylint.lint import Run

results = Run([path], do_exit=False)
final_score = results.linter.stats['global_note']

Finally, we evaluate the score…

if final_score < threshold:
    raise Exception()
else:
    exit(0)

In the full Gist code snippet above I use proper logging, outputs, and exception messages to make sure the runner is clear in what it is doing and in the final output!

Here are a few sample runs.

First we run the lint.py and it uses the default values and assume the source path as ./src and the score threshold as 7.

$ python lint.py

************* Module src.two
src/two.py:12:0: C0304: Final newline missing
------------------------------------------------------------------
Your code has been rated at 1.88/10 (previous run: 1.88/10, +0.00)
Exception: PyLint Failed | Score: 1.875 | Threshold: 7.0

You can also specify your threshold by using the parametrized arguments! In this example the code fails again and exits(1) because the code did not meet the threshold of 5.

$ python lint.py --path ./src --threshold 5

************* Module src.two
src/two.py:12:0: C0304: Final newline missing
------------------------------------------------------------------
Your code has been rated at 1.88/10 (previous run: 1.88/10, +0.00)
Exception: PyLint Failed | Score: 1.875 | Threshold: 5.0

If the code were to pass, like in the next example, it will exit(0) and all is well! Notice how the threshold argument can take a float like 1.5 in this case.

$ python lint.py --path ./src --threshold 1.5

************* Module src.two
src/two.py:12:0: C0304: Final newline missing
------------------------------------------------------------------
Your code has been rated at 1.88/10 (previous run: 1.88/10, +0.00)
PyLint Passed | Score: 1.875 | Threshold: 1.5

Bonus

Run with less verbose args.

$ python lint.py -p ./src -t 1.5

Get help if you forget how to run it!

$ python lint.py -h
optional arguments:
  -h, --help            show this help message and exit
  -p PATH, --path PATH  path to directory you want to run pylint | Default: ./src | Type: str
  -t THRESHOLD, --threshold THRESHOLD
                        score threshold to fail pylint runner | Default: 7 | Type: float

Personal Note

Real projects should expect much higher scores. My production projects usually are set to have 9 or 9.5 as the score threshold limit. However, I do use additional exclusions that differ from the base Pylint setup.

C0114, # missing-module-docstring
C0115, # missing-class-docstring
C0116, # missing-function-docstring
R0903  # too-few-public-methods

This snippet can be copy and pasted into the disable section of a .pylintrc file and it will ignore those errors and they will not lower your score.

The End

The code above and from this series can be found on Github!

doedotdev/wool

The next article talks about utilizing the python lint.py script and using it as a Github Action to automatically pass/fail builds based on code quality.

Pylint Static Code Analysis | Github Action to fail below a score threshold

The previous article in the series talks about running Pylint on the command line vs programatically.

Pylint Static Code Analysis | Executing with Command Line vs Programmatically

Thanks!