如何在Python中定义一个类的实例类字段？

class MyClass:
    def __init__(self, field1, field2):
        self.field1 = field1  # 实例字段
        self.field2 = field2  # 实例字段

# 创建类的实例
instance = MyClass("value1", "value2")

# 访问实例字段
print(instance.field1)  # 输出: value1
print(instance.field2)  # 输出: value2

class MyClass:
    class_field = "I am a class field"  # 类字段

    def __init__(self, instance_field):
        self.instance_field = instance_field  # 实例字段

# 创建类的实例
instance1 = MyClass("Instance 1 field")
instance2 = MyClass("Instance 2 field")

# 访问类字段
print(MyClass.class_field)  # 输出: I am a class field
print(instance1.class_field)  # 输出: I am a class field
print(instance2.class_field)  # 输出: I am a class field

# 修改类字段
MyClass.class_field = "Modified class field"

# 再次访问类字段
print(MyClass.class_field)  # 输出: Modified class field
print(instance1.class_field)  # 输出: Modified class field
print(instance2.class_field)  # 输出: Modified class field

# 修改实例字段
instance1.instance_field = "Modified instance field"

# 访问实例字段
print(instance1.instance_field)  # 输出: Modified instance field
print(instance2.instance_field)  # 输出: Instance 2 field