005_if语句

1、条件测试

car = "BMW"
print(car == "BMW") # 判断是否相等
print(car.lower() == "bmw") # 忽略大小写
print(car.lower() != "bmw") # 判断是否不相等
age = 18
height = 180
print(age == 18 and height == 180) # 所有条件为True结果才为True
print(age < 18 and height == 180) # and 只要有一个条件为False结果就为False
print(age < 18 or height == 180) # or 只要有一个条件为True结果就为True
ages = list(range(1, 21))
print(age in ages) # 判断变量在不在列表中
print(age not in ages) # 判断变量在不在列表中
game = True
over = False

2、if语句

# if语句
if ages:
    print("列表不为空")
ages = []
# if-else语句
if ages:
    print("列表不为空")
else:
    print("列表为空")
# if-elif-else语句
ages = list(range(1, 26))
for age in ages:
    if age < 3:
        name = "婴儿"
    elif age < 14:
        name = "小孩"
    elif age < 18:
        name = "少年"
    elif age >= 18:
        name = "成年人"
    else:
        name = "不可能触发else，else无意义可以省略，"
    print(f"{age}岁的你是一个{name}")

3、if语句处理列表、元组

current_users = ("Admin", "John", "Smith", "Pumbaa", "Clefariy")
print(type(current_users))
print(current_users)
new_users = ["john", "SMITH", "lisi", "root","ZHANGSAN"]
for new_user in new_users:
    if new_user.lower() in [value.lower() for value in current_users]: # 元组也可以用列表推导式
        print(f"用户名{new_user}已被使用")
    else:
        # 这里可以添加真正让用户名加入列表中，但我示例用的是元组，所以不可以操作
        # current_users.append(new_user)
        print(f"{new_user} 创建成功！")
print(current_users)

numbers = list(range(1, 10))
for number in numbers:
    if number == 1:
        print(f"{number}st")
    elif number == 2:
        print(f"{number}nd")
    elif number == 3:
        print(f"{number}rd")
    else:
        print(f"{number}th")