python基本操作（四）

与用户交互

为什么交互?

计算机取代人类，解放劳动力

如何交互

print('-'*100)

input('请输入你的姓名：')

print(""100)

python2和python3的交互(熟悉)

name = raw_input('请输入你的姓名：')
pwd = raw_input('请输入你的密码：')
print(type(name)) # 'str'
print(type(pwd)) # 'str'

格式化的输出

占位符

%s（针对所有数据类型）、%d（仅仅针对数字类型）

name = 'nick'
age = 19
print('my name is %s my age is %s' % (name, age))

my name is nick my age is 19

age = 19

print('my age is %d' % age)

my age is 19

format格式化

name = 'nick'
age = 19
print("hello, {}. you are {}.".format(name, age))

》 hello, nick. you are 19.

name = 'nick'
age = 19
print("hello, {1}. you are {0}-{0}.".format(age, name)

》hello, nick. you are 19-19.

f-string格式化

• name = "john"
  age = 19
  print(f"hello, {name}. you are {age}.")
• hello, john. you are 19.

大写的f也适用

• salary = 6.6666
  print(f'{salary:.2f}')
• 6.67

基本运算符

算术运算符

如：加减乘除

比较运算符

• pwd = '123'

  print(pwd != '123')

  print(pwd =='123')

  • false

  • true

赋值运算符

此处直接贴图了，以下假设变量a为10，变量b为20。

age = 19
age = age + 1
print(age)
20

age = 19
age *= 10
print(age)
190

逻辑运算符

此处直接贴图了，以下假设变量a为10，变量b为20。

# 从左到右的方式找到逻辑运算符，找到逻辑运算符的左边，左边成立，再去找到逻辑运算符的右边
print(3 > 3 and 1 > 2 or 2 > 1)  # false
true

身份运算符

身份运算符用于比较两个对象的存储单元

is和==的区别：is用于判断两个对象是否为同一个（是否在同一个内存空间），==用于判断引用变量得知是否相等。

x = 257
y = x
z = 257

print(f'x is y:{x is y}')
print(f'x == y:{x == y}')

print(f'x is z:{x is z}')
print(f'x == z:{x == z}')
x is y:true
x == y:true
x is z:false
x == z:true

python运算符优先级

python运算符的优先级是由括号决定的

链式赋值

a = 10
b = 10
c = 10
d = 10
print(f'a:{a}, b:{b}, c:{c}, d:{d}')
a:10, b:10, c:10, d:10
a = b = c = d = 10
print(f'a:{a}, b:{b}, c:{c}, d:{d}')
a:10, b:10, c:10, d:10

交叉赋值

x = 100
y = 200

temp = x
x = y
y = temp
print(f'x:{x}')
print(f'y:{y}')
x:200
y:100

x,y = y,x

print(f'x:{x}')

print(f'y:｛y}')

x:100

y:200

解压缩

name_list = ['nick', 'egon', 'jason']
x = name_list[0]
y = name_list[1]
z = name_list[2]
print(f'x:{x}, y:{y}, z:{z}')
x:nick, y:egon, z:jason

解压法

name_list = ['john', 'egon', 'jason',]

x,y,z = name_list

print（f'x:{x},y:{y},z:{z}')

x：john,y:egon,z:jason

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

字典也可以

info = {'name': 'nick', 'age': 18}
x, y = info
print(x, y)
name age