Refactor python system code

[dlimeng]

What is the purpose of the change

Related issues/PRs

Refactor python system code

181

Brief change log

Checklist

• [x] I have read the Contributing Guidelines on pull requests.
• [ ] I have explained the need for this PR and the problem it solves
• [ ] I have explained the changes or the new features added to this PR
• [ ] I have added tests corresponding to this change
• [ ] I have updated the documentation to reflect this change
• [ ] I have verified that this change is backward compatible
• [ ] If this is a code change: I have written unit tests to fully verify the new behavior.