如何使类的所有实例变量都是只读的?

假设我有一门课,如下所示:

class Test:
    def __init__(self, some_data_source):
        self.a = 5
        self.b = some_data_source['c']

data_source = {
    'c': 'some data'
}

x = Test(data_source)

# Should be illegal i.e result in an exception
x.a = 5
x.b = None

# This should be legal
print(x.a)

起初,我想 using properties ,但后来我意识到,为了动态地添加它们,我需要在定义类之后添加这些属性(例如 Test.attribute = property(...) __init__

否则如何使类的所有实例变量都是只读的?