Python: Replace mutable default arguments and prevent unintended side effects

[KanchiShimono]

Motivation and Context

Some functions and methods were using mutable objects (typically dict) as default argument values.
In Python, default arguments are evaluated only once at the time of function definition.
This can lead to unexpected behavior when the default value is modified within the function, as subsequent calls to the function may reuse the modified object.

As a result, calling such functions or methods multiple times can lead to unintended behavior.

Reference:
8.7. Function definitions (Official Python Documentation)

Default parameter values are evaluated from left to right when the function definition is executed. This means that the expression is evaluated once, when the function is defined, and that the same “pre-computed” value is used for each call. This is especially important to understand when a default parameter value is a mutable object, such as a list or a dictionary: if the function modifies the object (e.g. by appending an item to a list), the default parameter value is in effect modified. This is generally not what was intended. A way around this is to use None as the default, and explicitly test for it in the body of the function, e.g.:

Description

• Replaced mutable types (e.g., dict, list) used as default argument values with None, and properly initialized them within the function body.
• Reviewed and updated the parts of the code that performed destructive modifications on the arguments, to avoid unintentionally modifying variables from the caller’s scope.
• Added the flake8-bugbear rule in Ruff to detect this kind of issue.
  • For now, errors in tests and samples directories are ignored due to the large number of violations.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[moonbox3]

Thanks for the improvements, @KanchiShimono.

[markwallace-microsoft]

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3467	5 💤	0 ❌	0 🔥	1m 52s ⏱️

[KanchiShimono]

I’ve configured the project to ignore the Ruff rule (B009) that conflicts with mypy checks.
I also confirmed that the previously failing tests now pass in my local environment.