invalid-envvar-default (PLW1508)

Derived from the Pylint linter.

What it does

Checks for os.getenv calls with invalid default values.

Why is this bad?

If an environment variable is set, os.getenv will return its value as a string. If the environment variable is not set, os.getenv will return None, or the default value if one is provided.

If the default value is not a string or None, then it will be inconsistent with the return type of os.getenv, which can lead to confusing behavior.

Example

import os

int(os.getenv("FOO", 1))

Use instead:

import os

int(os.getenv("FOO", "1"))