这并不是因为它没有意义;将“x++”定义为“x+ = 1，求值到x的前一个绑定”非常有意义。

如果你想知道最初的原因，你必须在旧的Python邮件列表中寻找，或者询问当时在那里的人(例如。Guido)，但事后很容易就能证明:

简单的递增和递减不需要像其他语言那样多。你不会写这样的for(int i = 0;I < 10;i)在Python中经常使用;相反，你可以把I放在(0,10)范围内。

由于不经常需要它，所以没有理由给它自己的特殊语法;当您确实需要增加时，+=通常就可以了。

It's not a decision of whether it makes sense, or whether it can be done--it does, and it can. It's a question of whether the benefit is worth adding to the core syntax of the language. Remember, this is four operators--postinc, postdec, preinc, predec, and each of these would need to have its own class overloads; they all need to be specified, and tested; it would add opcodes to the language (implying a larger, and therefore slower, VM engine); every class that supports a logical increment would need to implement them (on top of += and -=).

这些都是+=和-=的冗余，所以会变成净损失。

我认为这与对象的可变性和不变性的概念有关。2,3,4,5在python中是不可变的。参考下图。2在此python进程之前有固定的id。

x++本质上意味着像C一样的原地增量。在C中，x++执行原地增量。因此，x=3, x++会将内存中的3增加到4，不像python中的3仍然存在于内存中。

因此，在python中，你不需要在内存中重新创建一个值。这可能会导致性能优化。

这是一个基于直觉的答案。

我相信这源于Python的信条“显式优于隐式”。

它就是这样设计的。自增和自减运算符只是x = x + 1的快捷方式。Python通常采用一种设计策略，减少执行操作的可选方法的数量。增强赋值是Python中最接近自增/自减操作符的东西，它们直到Python 2.0才被添加。

Maybe a better question would be to ask why do these operators exist in C. K&R calls increment and decrement operators 'unusual' (Section 2.8page 46). The Introduction calls them 'more concise and often more efficient'. I suspect that the fact that these operations always come up in pointer manipulation also has played a part in their introduction. In Python it has been probably decided that it made no sense to try to optimise increments (in fact I just did a test in C, and it seems that the gcc-generated assembly uses addl instead of incl in both cases) and there is no pointer arithmetic; so it would have been just One More Way to Do It and we know Python loathes that.

要完成那一页上已经很好的答案:

让我们假设我们决定这样做，前缀(++i)将打破一元的+和-操作符。

现在，用++或——作为前缀没有任何作用，因为它使一元加运算符两次(没有任何作用)或一元减运算符两次(两次:取消自身)

>>> i=12
>>> ++i
12
>>> --i
12

所以这可能会打破这个逻辑。

现在，如果需要它来进行列表推导或lambdas，从python 3.8开始，可以使用新的:=赋值操作符(PEP572)

预递增a并赋值给b:

>>> a = 1
>>> b = (a:=a+1)
>>> b
2
>>> a
2

后增量只需要通过减1来弥补过早的加法:

>>> a = 1
>>> b = (a:=a+1)-1
>>> b
1
>>> a
2