Python 访问控制

Java 中采用 public, protected, private 等修饰符来控制访问， Python 则采用命令约定来控制访问，一个下划线_开头表示保护方法，两个下划线__开头表示私有方法
Python 使用 @property 和 property setter 来控制属性的访问

import pytest


class Task:
    def __init__(self, note: str):
        self.note = note
        self._status = "created"

    # public method 公共方法
    def format_note(self) -> str:
        return self.note.title()

    # protected method 保护方法
    def _format_note(self) -> str:
        return self.note.title()

    # private method 私有方法
    def __format_note(self) -> str:
        return self.note.title()

    @property
    def status(self):
        return self._status

    @status.setter
    def status(self, value):
        allowed_values = ["created", "started", "completed", "suspended"]
        if value in allowed_values:
            self._status = value
            print(f"task status set to {value}")
        else:
            print(f"invalid status: {value}")


def test_class_access():
    task = Task(note="python book")
    assert task.format_note() == "Python Book"
    assert task._format_note() == "Python Book"
    with(pytest.raises(AttributeError)):
        assert task.__format_note() == "Python Book"

    # __private_method -> _ClassName__private_method
    # 使用 _ClassName__private_method 访问私有方法
    assert task._Task__format_note() == "Python Book"