Python3中的赋值语句_3x=y是python赋值语句吗-优快云博客

本文深入探讨Python中的各种赋值语句，包括基础赋值、元组赋值、列表赋值、序列赋值、序列解包、多目标赋值及增量赋值，通过实例详细解析每种赋值方式的特点和应用场景。

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Python中的赋值语句就是把对象赋值给变量，基本形式是在等号左侧写赋值语句的目标，要赋值的对象则位于等号右侧；等号左侧是对象或对象组件，等号右侧可以是任何通过计算能得到对象的表达式；赋值语句总是创建对象的引用，而不是复制对象；

Python3中赋值语句有如下形式：

赋值语句形式：

运算	解释
s = 'ixusy88'	基础形式
s1,s2 = '123','abc'	元组赋值
[s1,s2] = ['123','abc']	列表赋值
a,b,c = '123'	序列赋值
a,*b = 'ixusy88'	序列解包
a=b= 'ixusy88'	多目标赋值
a += 22	增量赋值(等价于 a = a + 22)
隐式赋值	模块导入，函数和类定义，for循环变量，函数参数等

1:基础形式

>>> s='ixusy88'
>>> s
'ixusy88'
>>>

2：元组赋值

>>> (s1,s2) = ('123','abc')
>>> s1,s2
('123', 'abc')
>>> 
#也可以不需要括号()
>>> s1,s2 = '111','cccc'
>>> s1,s2
('111', 'cccc')
>>> 
# 左边与右边的元素个要一致，不然会报错，如下：
>>> s1,s2 = '111','222','333'
Traceback (most recent call last):
  File "<pyshell#20>", line 1, in <module>
    s1,s2 = '111','222','333'
ValueError: too many values to unpack (expected 2)
>>>

3：列表赋值

>>> [a,b] = ['123','abc']
>>> a,b
('123', 'abc')
>>> 
# 
>>> a,b = ['123','abc']
>>> a,b
('123', 'abc')
>>> 
# 等号右边可以是元组
>>> [a,b] = '123','abc'
>>> a,b
('123', 'abc')
# 等号 两边元素需要一致
>>> [a,b,c] = ['123','abc']
Traceback (most recent call last):
  File "<pyshell#56>", line 1, in <module>
    [a,b,c] = ['123','abc']
ValueError: not enough values to unpack (expected 3, got 2)
>>> [a,b] = ['123','abc','444']
Traceback (most recent call last):
  File "<pyshell#57>", line 1, in <module>
    [a,b] = ['123','abc','444']
ValueError: too many values to unpack (expected 2)
>>>

4：序列赋值

>>> a,b,c,d = '1234'
>>> a,b,c,d
('1', '2', '3', '4')
>>> 
# 等号两边元素要一致
>>> a,b,c,d = '123'
Traceback (most recent call last):
  File "<pyshell#91>", line 1, in <module>
    a,b,c,d = '123'
ValueError: not enough values to unpack (expected 4, got 3)
>>> a,b,c = '1234'
Traceback (most recent call last):
  File "<pyshell#92>", line 1, in <module>
    a,b,c = '1234'
ValueError: too many values to unpack (expected 3)
>>>

5：序列解包

# 带星号的名称，会被赋值一个列表，该列表收集了序列中剩下的没被赋值给其他名称的所有项
>>> a,*b = 'ixusy88'
>>> a,b
('i', ['x', 'u', 's', 'y', '8', '8'])
>>> a,*b,c = 'ixusy88'
>>> a,b,c
('i', ['x', 'u', 's', 'y', '8'], '8')
>>> 
>>> a,*b = [1,2,3,4]
>>> a,b
(1, [2, 3, 4])
>>> a,*b,c = [1,2,3,4,5]
>>> a,b,c
(1, [2, 3, 4], 5)
>>> 
>>> a,*b,c = range(5)
>>> a,b,c
(0, [1, 2, 3], 4)
>>> a,*b,c = [1,2,3]
>>> a,b,c
(1, [2], 3)
>>>

6：多目标赋值

# 三个变量指向了同一个对象
>>> a=b=c = 'ixusy88'
>>> a,id(a)
('ixusy88', 2197246939464)
>>> b,id(b)
('ixusy88', 2197246939464)
>>> c,id(c)
('ixusy88', 2197246939464)
>>>

7：增量赋值

增量赋值语句有：

x += y x &= y x -= y x |= y

x *= y x ^= y x /= y x >>= y

x %= y x<<= y x **= y x //= y

# "+=" 对列表而言是在原位置修改：
a = [1,2,3]
b = [3,4,5]

print('1----',id(a),a)
print('2----',id(b),b)
a+=b
print('3----',id(a),a)

print('*'*10)
# "+" 是拼接，会产生新的对象：
x = [10,20,30]
y = [30,40,50]
print('4----',id(x),x)
print('5----',id(y),y)
x = x + y
print('6----',id(x),x)