Who can access my data?
Most object-oriented programming languages have a concept of "access control". This is related to abstraction. Some attributes and methods on an object are marked "private", meaning only that object can access them. Others are marked "protected", meaning only that class and any subclasses have access. The rest are "public", meaning any other object is allowed to access them.
Python doesn't do that. Python doesn't really believe in enforcing laws that might someday get in your way. Instead, it provides unenforced guidelines and best practices. Technically, all methods and attributes on a class are publicly available. If we want to suggest that a method should not be used publicly, we can put a note in docstrings indicating if a method is meant for internal use only, (preferably with an explanation of how the public-facing API works!).
By convention, we can also prefix an attribute or method with an underscore character: _. Most Python programmers will interpret this...
