User interaction, operator

User interaction, operator

First, the interaction with the user

• User interaction is the person to the computer input / input data, the computer print / output (essentially the input, output)
• python2 you must declare the type of input
• python3 accept user input, no matter what type of user input, the final return must be a string

pyton3

input('name:')
name：Yang
'Yang' 

python2

raw_input('name:')
name:Yang
'Yang'

• python2 in raw_input and python3 the input function is exactly the same

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Second, formatted output

Placeholder 1.% s: you can receive any type of variable

% D placeholder: receiving a digital only type

Example 1:

print('亲爱的%s您好！您%s月的话费是%d，余额还有%d' %('Tony',11,83,1))
亲爱的Tony您还！您11月的话费是83，余额还有1

Example 2:

>>> name = 'yang'
>>> age = 22
>>> hobby = 'play, money'
>>> print('my name is %s, my age is %d,my hobby is %s' %(name, age, hobby))
my name is yang, my age is 22,my hobby is play, money

Two decimal places: '.% 2f'

>>> a = 3.1415926
>>> print('%.2f' %a)
3.14

2. .format

username = 'Yang'
ages = 22
print('name:{user},age:{age}'.format(user=username,age=ages))
name:Yang,age:22

3.f-string

name = 'chen'
age = 18
hobby = 'yang'
print(f'姓名:{name}，年龄:{age},爱好:{hobby}') 
姓名:chen，年龄:18,爱好:yang

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Third, the operator

• Arithmetic Operators

• Comparison Operators

• Assignment Operators

  • Incremental assignment x = 10 x + = 1 (x = x + 1)
    

  • Chain assignment x = y = z = 10

  • CROSS assignment m = 1, n = 2 m, n = n, m

  • Decompression assignment

  >>> L1=[1,2,3,4,5]
  >>> a,b,c,d,e=L1
  >>> a,b,c,d,e
  (1, 2, 3, 4, 5)
  #如果变量名少了或者多了，都会报错
  >>> a,b,*_=L1 #取头尾的几个值，可以用*_
  >>> a,b
  (1, 2)

• Logical Operators

  and

  or

  not

• Member operator

  in

  not in
  

>>> 'hello' in 'hello world!'
True
>>> 'hello' not in 'hello world!'
False

• Identity operator
  

>>> x=y=10
>>> id(x)
1737518848
>>> id(y)
1737518848
>>> x is y
True
>>> x is not y
False