融入python-6-赋值

变量赋值

x,y,z = 1,2,3

灵活使用，可以减少代码量

key,value = dict.popitem()

*星号的使用可以代表多个值

#正常

x,y,z = 1,2,3  

#参数列表数目不匹配

x,y,z = 1,2,3,4
Traceback (most recent call last):
File "<input>", line 1, in <module>
ValueError: too many values to unpack (expected 3)
x,y,z = 1,2
Traceback (most recent call last):
File "<input>", line 1, in <module>
ValueError: not enough values to unpack (expected 3, got 2)

#星号来收集

x,y,*z = 1,2,3,4
z
[3, 4]

#两个星号不可以！

*x,y,*z = 1,2,3,4,5,6
File "<input>", line 1
SyntaxError: two starred expressions in assignment

链式赋值

x = y = z = '你好，中国'

运算赋值

+=  -=  *=  /=

x
1
x += 3
x
4
x -= 1
x
3
x *= 7
x
21
x /= 9
x
2.3333333333333335

字符串运算

x = "你好"
x
'你好'
x += "，悟空。"
x
'你好，悟空。'
x -= "哈哈"
Traceback (most recent call last):
  File "<input>", line 1, in <module>
TypeError: unsupported operand type(s) for -=: 'str' and 'str'
x -= "空。"
Traceback (most recent call last):
  File "<input>", line 1, in <module>
TypeError: unsupported operand type(s) for -=: 'str' and 'str'
x *= "哈哈"
Traceback (most recent call last):
  File "<input>", line 1, in <module>
TypeError: can't multiply sequence by non-int of type 'str'
x *= 2
x
'你好，悟空。你好，悟空。'
x /= 3
Traceback (most recent call last):
  File "<input>", line 1, in <module>
TypeError: unsupported operand type(s) for /=: 'str' and 'int'