《Python编程：从入门到实践》 第五章 笔记

第五章 IF语句

a =5

ifa ==6:

print("yes")

else:

print("no")

no

5.2.6 　检查特定值是否包含在列表中

mvp_candidate = ["Irving","Harden","Jmaes","Durant"]

mvp ="Irving"

ifmvpinmvp_candidate:

print("True")

else:

print("False")

True

5.2.7 　检查特定值是否不包含在列表中

mvp_candidate = ["Irving","Harden","Jmaes","Durant"]

DOY ="Horford"

ifDOYnot inmvp_candidate:

print(DOY +"is the best defender of the year")

else:

print("It's OK!")

Horfordis the best defender of the year

5.2.8 　布尔表达式

mvp ='Irving'

print(mvp =='Irving')

print(mvp =='James')

True

False

mvp ='Irving'

print(mvp =='Irving'.lower())

False

mvp ='Irving'

doy ='Horford'

print(mvp =='Irving'anddoy =='Horford')

True

a =5

b =7

print(a >5andb

False

mvp_candidate = ["Irving","Harden","Jmaes","Durant"]

print('Irving'inmvp_candidate)

True

mvp_candidate = ["Irving","Harden","Jmaes","Durant"]

print('Irving'not inmvp_candidate)

False

5.3.3 　 if-elif-else 结构

age =12

ifage ==18:

print("Bad news!You have became an audlt.")

elifage >18:

print("Keep working hard,you know what I mean.")

else:

print("You can still enjoy your time.")

You can still enjoy your time.

5.3.5 　省略 else 代码块

else 是一条包罗万象的语句，只要不满足任何 if 或 elif 中的条件测试，其中的代码就会执行，这可能会引入无效甚至恶意的数据。如果知道最终要测试的条件，应考虑使用一个 elif 代码块来代替 else 代码块。这样，你就可以肯定，仅当满足相应的条件时，你的代码才会执行。

age =12

ifage ==18:

print("Bad news!You have became an audlt.")

elifage >18:

print("Keep working hard,you know what I mean.")

elifage

print("You can still enjoy your time.")

You can still enjoy your time.

5.3.6 　测试多个条件

Celtics = ['Irving','Harward','Horford']

if'Irving'inCeltics:

print("Irving is a Celtics!")

if'Horford'inCeltics:

print("Horford is a Celtics!")

if'Harward'inCeltics:

print("Harward is a Celtics!")

print("They will be the champion!")

Irving is a Celtics!

Horford is a Celtics!

Harward is a Celtics!

They will be the champion!

Celtics = ['Irving','Harward','Horford']

if'Irving'inCeltics:

print("Irving is a Celtics!")

elif'Horford'inCeltics:

print("Horford is a Celtics!")

elif'Harward'inCeltics:

print("Harward is a Celtics!")

print("They will be the champion!")

Irving is a Celtics!

They will be the champion!

if-if-if，在符合一个条件后他会继续去判断下一个条件

if-elif-else，在符合一个条件后不会去判断下一个条件，直接跳出循环。

5.4.2 　确定列表不是空的

Celtics = []

ifCeltics:

forCelinCeltics:

print("Yes,"+ Cel +" is a Celtics!")

print("thank you for use!")

else:

print("do you know anyone in Celtics?")

do you know anyone in Celtics?

5.4.3 　使用多个列表

automatic_rifle = ['M4A1','M16A4','SCAR','AK47','GROZA']

fav_automatic_fifle = ['M4A1','M16A4','SCAR']

forautomatic_rifleinfav_automatic_fifle:

ifautomatic_rifleinfav_automatic_fifle:

print("5.56")

else:

print("7.62")

print("WINNER WINNER ,CHICKEN DINNER!")

5.56

5.56

5.56

WINNER WINNER ,CHICKEN DINNER!

大于 >=

小于