链式作业如何工作? [英] How do chained assignments work?

问题描述

引用某事:

<预><代码>>>>x = y = 某个函数()

与

相同<预><代码>>>>y = 某个函数()>>>x = y

问题:是

x = y = somefunction()

与

相同

x = somefunction()y = 某个函数()

?

根据我的理解，它们应该是一样的，因为 somefunction 只能返回一个值.

解决方案

如果 somefunction 返回可变值，它们的工作方式不一定相同.考虑:

<预><代码>>>>def somefunction():... 返回 []...>>>x = y = 某个函数()>>>x.append(4)>>>X[4]>>>是[4]>>>x = 某个函数()；y = 某个函数()>>>x.append(3)>>>X[3]>>>是[]

A quote from something:

>>> x = y = somefunction()

is the same as

>>> y = somefunction()
>>> x = y

Question: Is

x = y = somefunction()

the same as

x = somefunction()
y = somefunction()

?

Based on my understanding, they should be same because somefunction can only return exactly one value.

解决方案

They will not necessarily work the same if somefunction returns a mutable value. Consider:

>>> def somefunction():
...     return []
... 
>>> x = y = somefunction()
>>> x.append(4)
>>> x
[4]
>>> y
[4]
>>> x = somefunction(); y = somefunction()
>>> x.append(3)
>>> x
[3]
>>> y
[]

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