如何将变量从一个类传递到另一个类？

class ClassA:
    def __init__(self, variable):
        self.variable = variable

class ClassB:
    def __init__(self):
        variable = "Hello"
        self.instance_of_a = ClassA(variable)

b = ClassB()
print(b.instance_of_a.variable)  # 输出：Hello

class ClassA:
    pass

class ClassB:
    def __init__(self):
        self.variable = "Hello"

a = ClassA()
b = ClassB()
a.variable = b.variable

print(a.variable)  # 输出：Hello

class ClassA:
    def method(self, variable):
        self.variable = variable

class ClassB:
    def __init__(self):
        self.variable = "Hello"

a = ClassA()
b = ClassB()
a.method(b.variable)

print(a.variable)  # 输出：Hello