第七章 用户输入和while 循环

7.1 创建多行字符串的方式：

01 prompt="if you tell me who you are, we can personalize the message you see."

02 prompt+="what is your first name? ";

03

04 name=input(prompt);

05 print(" hello,"+name+'!');

>>>

if you tell me who you are, we can personalize the message you see.what is your first name? franz

   

hello,franz!

7.2 使用函数int()获得整数输入

01 height = input("How tall are you, in inches? ")

02 height = int(height)

03 if height >= 36:

04 print(" You're tall enough to ride!")

05 else:

06 print(" You'll be able to ride when you're a little older.")

>>>

How tall are you, in inches? 20

   

You'll be able to ride when you're a little older.

7.3 求模运算

目的：求模运算符 （%） 是一个很有用的工具， 它将两个数相除并返回余数

01 number = input("Enter a number, and I'll tell you if it's even or odd: ")

02 number = int(number)

03 if number % 2 == 0:

04 print(" The number " + str(number) + " is even.")

05 else:

06 print(" The number " + str(number) + " is odd.")

>>>

Enter a number, and I'll tell you if it's even or odd: 45

   

The number 45 is odd.

7.4 while 循环：

• 目的：for 循环用于针对集合中的每个元素都一个代码块， 而while 循环不断地运行， 直到指定的条件不满足为止
• 使用标志判定程序的活动状态：

01 prompt=" Tell me sth,and I will repeat back to you";

02 prompt+=" Enter 'quit' to end the program. ";

03 act=True;

04 while act:

05 message=input(prompt);

06 if message=='quit':

07 act=False;

08 else:

09 print(message);

>>>

Tell me sth,and I will repeat back to you

Enter 'quit' to end the program. no

no

   

Tell me sth,and I will repeat back to you

Enter 'quit' to end the program. yes

yes

   

Tell me sth,and I will repeat back to you

Enter 'quit' to end the program. quit

• break语句与continue语句：

01 # Break test & continue tst

02

03 prompt=" Tell me sth,and I will repeat back to you";

04 prompt+=" Enter 'quit' to end the program. ";

05 while True:

06 message=input(prompt);

07 if message=='quit':

08 break;

09 else:

10 print(message);

11

12

13 current_number = 0

14 while current_number < 10:

15 current_number += 1

16 if current_number % 2 == 0:

17 continue

18 print(current_number)

>>>

Tell me sth,and I will repeat back to you

Enter 'quit' to end the program. quit

1

3

5

7

9

• 删除包含特定值的所有列表元素（方法remove()与关键词del）

01 # test:remove specific element

02

03 # tip1:remove()

04 pets = ['dog', 'cat', 'dog', 'goldfish', 'cat', 'rabbit', 'cat'];

05 while 'cat' in pets:

06 pets.remove('cat');

07 print(pets);

08

09 # tip2:del

10 pets = ['dog', 'cat', 'dog', 'goldfish', 'cat', 'rabbit', 'cat'];

11 index=0;

12 while 'cat' in pets:

13 if pets[index]=='cat':

14 del pets[index];

15 index=index;

16 else:

17 index+=1;

18 print(pets);

19

20 # tip1 is better than tip2

>>>

['dog', 'dog', 'goldfish', 'rabbit']

['dog', 'dog', 'goldfish', 'rabbit']

• 使用用户输入填充