IF语句

等值检验

# 等值检验 (==必须使用双等号)(!=代表不等检验)
name = 'jody'
if name == 'jody':
    print('hello,jody!')
elif name != 'jody':
    print('who are you')
--------------------------------------
hello,jody!

names = ['Anan','Jody','John','wang']
for name in names:
    if name == 'wang':
        print(name.upper())
    elif name.lower() == 'jody':
        print(name.title())
    elif name.upper() == 'ANAN':
        print(name)
    else:
        print('you may be '+name)
------------------------------------------
Anan
Jody
you may be John
WANG

• IF语句可以使用and,or语句来增加检验条件
• else是一条保罗万象但并非必须具备的语句，只要不满足if和elif中的条件，else就会被执行，即使在输入错误的情况下。因此，若知道else语句具体指那种条件，应该使用elif语句。

available_toppings = ['mushroom','olives','green peppers',
                      'pepperoni','pineapple']
request_toppings = ['mushroom','fries','cheese']
for request_topping in request_toppings:
    if request_topping in available_toppings:
        print('a '+request_topping)
    else:
        print("sorry,we don't have this")
------------------------------------------------
a mushroom
sorry,we don't have this
sorry,we don't have this    

• 这两个表的if检验挺有意思。

数值比较

ages = list(range(7,9))
for age in ages:
    if age <= 8:
            print(age)
    elif age in [9,20]:
        print(age-1)
    elif age >= 20:
        print(age-10)
----------------------------------------------
7
8

小结

• if 与 for 循环的结合；
• if 与 .title() .upper() .lower() 的结合；
• if 判断语句的等值(==)，不等(!=)以及其他数值判断符号(>,>=,<,<=)。