# 值为 False 的表达式包括：
# False   None   0   ""   ()   []   {}
# 其他值都视为 True
# True 和 False 不过是 0 和 1 的别名

print(bool(None))  # False
print(True == 1)  # True
print(True == 2)  # False
print(False == 0)  # True
print(False + True + 2)  # 3

# 条件表达式，类似于三目运算符
a = True
b = "a" if a else "b"
print(b)  # a


if True:
    """"""  # 用一个字符串来起到空语句的作用

if True:
    pass  # 空语句

x = [1, 2, 3]
y = [1, 2, 3]
z = x

# 相等
if x == y:
    print("x=y")  #
else:
    print("x!=y")

# x和y是同一个对象
if x is y:
    print("x is y")
else:
    print("x is not y")  #

# x和y不是同一个对象
if x is not z:
    print("x is not z")
else:
    print("x is z")  #

# 1是容器（如序列）x的成员
if 1 in x:
    print("1 in x")  #
else:
    print("1 not in x")

# 2不是容器（如序列）x的成员
if 2 not in x:
    print("2 not in x")
else:
    print("2 in x")  #

x = "abc"
y = "def"
z = x or y
print(z)  # abc

x = "abc"
y = "def"
z = x and y
print(z)  # def

x = None
y = "def"
z = x and y
print(z)  # None

y = "def"
z = not y
print(z)  # False


# 链式比较
a = 3
if 0 <= a <= 9:
    print("ok")

# 断言
age = 10
assert 0 < age

# 断言测试不通过时将抛出异常
try:
    age = -1
    assert 0 < age, "年龄必须为整数"
except Exception as e:
    print(e)  # 年龄必须为整数

x = 0
y = 1
assert x < y  # 通过
assert x or y  # 通过
# assert x and y   #异常