格式化输出与基本运算符

一 python与用户的交互

1 如何交互

可以通过input()和print()来实现简单的交互，input()方法的作用只是接收值,无论我们输入的值是任何类型，input()接收的都是字符串。

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    input('name:')
    input('age:')

name:einsam
age:18

'18'

2 python2的input和raw_input

python2的raw_input就是python3的input
python2中的input与用户交互时必须得用户指定输入内容的数据类型，现在python写的程序都是与用户交互，所以它没有存在的必要了。

二 格式化输出

1 占位符

用逗号进行字符串拼接非常麻烦，这时候就需要用到占位符 %s 和 %d

name = input('name:')
age = input('age:')
print ('my name is %s,my age is %s '% (name,age))

name:einsam
age:11
my name is einsam,my age is 11

2 format格式化

name = input('name:')
age = input('age:')
print('my name is {}, my age is {}'.format(name,age))

name:einsam
age:11
my name is einsam, my age is 11

name = input('name:')
age = input('age:')
print('my name is {0}, my age is {1}'.format(name,age))

name:einsam
age:11
my name is einsam, my age is 11

name = input('name:')
age = input('age:')
print('my name is {name}, my age is {age}'.format(name=name,age=age))

name:einsam
age:11
my name is einsam, my age is 11

3 f-String格式化

name = input('name:')
age = input('age:')
print(f'my name is {name}, my age is {age}')

name:einsam
age:11
my name is einsam, my age is 11

f大小写都是可以的

三 基本运算符

1 算数运算符

1+1

2

1-1

0

1*1

1

1/1

1.0

1//1

1

2 比较运算符

1>1

False

1<1

False

1!=1

False

1>=1

True

1<=1

True

3 赋值运算符

x = 1
print(x)

1

4 逻辑运算符

and or not

2 > 1 and 3 > 2

True

2 > 1 or 1 > 2

True

not 2 > 1

True

5 身份运算符

is 比较的是 id

x = 10 
y = 10
print(x is y)
print(x == y)

True
True

x = 1000 
y = 1000
print(x is y)
print(x == y)

False
True

x = 100
y = 10
print(x is y)
print(x == y)

False
False

id相同的值一定相同，值相同的id不一定相同，小整数池的除外

6 python运算优先级

想要优先级高的，用括号括起来就行了

7 链式赋值

x = 1
y = 1 
z = 1
print(x,y,z)

1 1 1

x = y = z
print(x,y,z)

1 1 1

7 交叉赋值

x = 10
y = 11

z = x
x = y
y = z
print(x,y)

11 10

8 解压缩

解压缩就是把多个值一次性拿出来

有时候我们解压缩的值可能是我们不想要的，那么可以使用下划线，万能的下划线。

name_list = ['nick', 'egon', 'jason', 'tank', 'kevin', 'jerry']
x, y, _, _, _, z = name_list
print(x,y,z)

nick egon jerry

*_可以省略多个我们不需要的值

name_list = ['nick', 'egon', 'jason', 'tank', 'kevin', 'jerry']
x, y, *_, z = name_list
print(x,y,z)

nick egon jerry