obj_x = [10, 20]
obj_y = [10, 20]
print(obj_x == obj_y)  # True 比较内容
print(obj_x is obj_y)  # False 比较内存地址


# 定义一个列表，并让另一个变量引用它
obj_p = [30, 40]
obj_q = obj_p  # obj_q 引用了 obj_p 所指向的同一个对象
print(obj_p == obj_q)  # True 比较内容
print(obj_p is obj_q)  # True 比较内存地址


# is not None 判断一个变量是否为None
my_variable = None

if my_variable is not None:
    # 如果 my_variable 不是 None，则打印此消息
    print("Variable is not None")
else:
    # 如果 my_variable 是 None，则打印此消息
    print("Variable is None")

#  错误示范：使用 != None 进行比较
# if my_variable != None:
# 如果 my_variable 不等于 None，则打印此消息
# print("Variable is not None (using != None)")


sum = 0
for i in range(5):
    if i == 2:
        continue
    sum += i

print(sum)