python赋值

1、直接赋值

>>> y = 1
>>> x = (1,'one')
>>> z = ['age',18]
>>> o = 'strong'
>>> y
1
>>> x
(1, 'one')
>>> z
['age', 18]
>>> o
'strong'

>>> d = {'name':'Hiden'}
>>> d
{'name': 'Hiden'}

2、解包赋值,常用于函数或者方法返回元组（或其他序列或可迭代对象）时

>>> x,y,z = (1,2,3)
>>> x
1
>>> y
2

>>> z
3

>>> dic = {'age':18,'addr':'BeiJing'}
>>> k,v = dic.popitem()
>>> k
'addr'
>>> v
'BeiJing'

###带*号的变量解包

>>> a,b,*res = (1,2,3,4)
>>> a
1
>>> b
2
>>> res  ###list格式
[3, 4]

####注意：解包的序列元素数量要与=左边的变量数量完全一致，否则会报错

>>> x,y,z = 1,2
Traceback (most recent call last):
File "<pyshell#128>", line 1, in <module>
x,y,z = 1,2
ValueError: not enough values to unpack (expected 3, got 2)
>>> x,y = 1,2,3
Traceback (most recent call last):
File "<pyshell#129>", line 1, in <module>
x,y = 1,2,3
ValueError: too many values to unpack (expected 2)

3、链式赋值

>>> x = y =somefunction()

但是不一定等同于

x=somefunction()

y=somefunction()

4、增量赋值

x+=1（-、%、/等标准运算符也适用）

对于其他数据类型也适用，只要二元运算符适用于这些数据结构即可：

>>> fnord = 'foo'
>>> fnord +='bar'
>>> fnord*=2
>>> fnord
'foobarfoobar'