Python第四天学习笔记

Python的用户交互

input('请插入vip卡')
input('输入密码')

请插入vip卡23333
输入密码6666





'6666'

print('*'*100)

****************************************************************************************************

print('*'*100)

input('请插入vip卡')

print('-'*100)

****************************************************************************************************
请插入vip卡6666
----------------------------------------------------------------------------------------------------

• input只是一个学习交互过渡用的，一般的用户交互是不会用到input的

vip_card = input('请插入vip卡')
print(vip_card)

请插入vip卡88888888
88888888

• 无论你输入的是什么，input接受的都是字符串

vip_card = input('请输入vip卡')
print(vip_card)
print(type(vip_card))

请输入vip卡123456789
123456789
<class 'str'>

age = input('请输入你的年龄')
print(age)

age = int(age)  #将age由字符串转变为整型,当然这个字符串必须本来就是个数字
print(type(age))

请输入你的年龄22
22
<class 'int'>

Python2的input和raw_input(了解)

Python2的raw_input就是Python3的input

Python2中的input如果要是输入的是一个字符串，比如yang_height，它是分不清是字符串还是变量名的，此时需要声明数据类型

格式化输出

利用占位符

name = input('name:>>>')
age = input('age:>>>')
age = int(age)
height = input('height:>>>')

# %s就是字符串类型的占位，后面的%()就是对应前面的占位
print('My name is %s,My age is %s,My height is %s'%(name,age,height))

name:>>>yang
age:>>>22
height:>>>180
My name is yang,My age is 22,My height is 180

name = input('name:>>>')
name = int(name)

age = input('age:>>>')
age = int(age)

height = input('height:>>>')
height = int(height)

# %d是整型占位符，后面的%()也应该是整型
print('My name is %d,My age is %d,My height is %d'%(name,age,height))

name:>>>1
age:>>>1
height:>>>1
My name is 1,My age is 1,My height is 1

format格式化（了解）

name = input('name:>>>')
age = input('age:>>>')
height = input('height:>>>')

#print('My name is %s,My age is %s,My height is %s'%(name,age,height)) 占位符占位
print('My name is {},My age is {},My height is {}'.format(name,age,height))

name:>>>yang
age:>>>22
height:>>>180
My name is yang,My age is 22,My height is 180

print('My name is {0},My age is {1},My height is {2}'.format(name,age,height))

My name is yang,My age is 22,My height is 180

print('My name is {0},My age is {0},My height is {0}'.format(name,age,height))

My name is yang,My age is yang,My height is yang

print('My name is {age},My age is {name},My height is {height}'.format(name=name,age=age,height=height))

My name is 22,My age is yang,My height is 180

f-string格式化

name = input('name:>>>')
age = input('age:>>>')
height = input('height:>>>')

#print('My name is %s,My age is %s,My height is %s'%(name,age,height)) 占位符占位
#print('My name is {},My age is {},My height is {}'.format(name,age,height)) format格式化
print(f'My name is {age},My age is {name},My height is {height}')

name:>>>yang
age:>>>22
height:>>>180
My name is 22,My age is yang,My height is 180

f-string的内部占位还可以进行运算，更加方便

print(f'My name is {name},My age is{int(age)+1},My height is {height*10}')

My name is yang,My age is23,My height is 180180180180180180180180180180

print(f'My name is {name},My age is{int(age)+1},My height is {int(height)*10}')

My name is yang,My age is23,My height is 1800

print(f'My name is {name},My age is{int(age)+1:.5f},My height is {int(height)*10}')

My name is yang,My age is23.00000,My height is 1800

注：:.3f是保留三位小数

基本运算符

算数运算符

1 + 1

2

1 - 1

0

1*1

1

1/1

1.0

1%1 #取余数

0

72//6 #向下取整

12

比较运算符

1 > 1

False

1 < 1

False

1 >= 1

True

1 <= 1

True

1 == 1 #注意这里是双等号

True

1 = 1 #单等号是赋值，会报错

  Cell In[36], line 1
    1 = 1 #单等号是赋值，会报错
    ^
SyntaxError: cannot assign to literal here. Maybe you meant '==' instead of '='?

1 != 1

False

逻辑运算符

• and
• or
• not

1 <= 1 and 1 >= 1

True

1 > 1 and 1 <= 1

False

1 > 1 or 1 <= 1 

True

not'张洋很帅'

False

身份运算符

is 比较的是id

x = 10
y = 10
print(x is y) # 因为小整数池的原因，结果是True
print(x == y)

True
True

x = 257
y = 257
print(x is y)
print(x == y)

False
True

id相同的值一定相同，值相同的id不一定相同，除了小整数池的除外

Python运算符优先级

想优先直接加括号()就OK

链式赋值

x = y = z =10
print(x,y,z)

10 10 10

交叉赋值

x = 10
y = 20

z = x 
x = y 
y = z #就是找个新的变量来储存，在其他编程语言中也常见
print(x,y)

20 10

# Python中特有的方式
x = 10
y = 20
x,y =y,x
print(x,y)

20 10

解压缩

hobby_list = ['run','read','swimming','music','go']
print(hobby_list(3)) #记住是[3],不是(3)

---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

Cell In[48], line 2
      1 hobby_list = ['run','read','swimming','music','go']
----> 2 print(hobby_list(3))


TypeError: 'list' object is not callable

hobby_list = ['run','read','swimming','music','go']
#               0      1       2         3      4
print(hobby_list[3])

music

hobby_list = ['run','read']
hobby1,hobby2 = hobby_list
print(hobby1)
print(hobby2)

run
read

hobby_list = ['run','read','swimming','music','go']
_,hobby1,_,_,hobby2 = hobby_list
print(hobby1)
print(hobby2)

read
go

hobby_list = ['piao','666',2333,999,'handsome','read','piao','666',2333,999,'handsome','read']
# *_相当于把后面都占了
_,hobby1,_,hobby2,*_ = hobby_list
print(hobby1)
print(hobby2)

666
999

hobby_list = ['piao','666',2333,999,'handsome','read','piao','666',2333,999,'handsome','read']
hobby1,*_,hobby2 = hobby_list # *_把中间都吃了
print(hobby1)
print(hobby2)

piao
read

结束，睡觉