[英]Is 'this' the cpp equivalent of 'self' in python?
I'm experienced in Python and now learning cpp to speed up code.我在 Python 方面很有经验,现在正在学习 cpp 来加速代码。 After reading a bit
this
seems to be the cpp equivalent of self
.读了一点之后,
this
似乎是self
的 cpp 等价物。 I found a question explaining the difference from a cpp user's point of view but I'd like to know any differences for a python user's point of view.我发现了一个问题,从 cpp 用户的角度解释了差异,但我想知道 python 用户的观点有什么不同。
The major difference is that you mostly don't need this
in C++, because there is a syntactic distinction between defining a member and referring to it.主要区别在于您在 C++ 中通常不需要
this
,因为定义成员和引用成员之间存在语法区别。
Contrast对比
Python: Python:
class Foo:
def __init__(self):
self._bar = 42
def baz(self):
return self._bar += 1
C++: C++:
class Foo {
int bar = 42;
public:
int baz() { return bar += 1; }
}
In addition to the answer already given, self
in Python is just a conventional name chosen for the first argument of a class method which refers to the object itself that the method is called on directly.除了已经给出的答案之外,Python 中的
self
只是为类方法的第一个参数选择的常规名称,该名称指的是直接调用该方法的对象本身。
In C++, this
is a keyword that is not explicitly specified as a parameter of a non-static class member function, but automatically refers to the instance that such a function is called on as pointer .在 C++ 中,
this
是一个关键字,没有明确指定为非静态类成员函数的参数,但会自动将调用此类函数的实例作为指针引用。
That means this
is not a reference to the object, but a pointer to it.这意味着
this
不是对对象的引用,而是指向它的指针。 So所以
this.member = 4;
is not possible.不可能。
this
must be dereferenced first to obtain a reference to the object from the pointer:必须首先取消引用
this
才能从指针获取对对象的引用:
this->member = 4;
or (uncommonly)或(不常见)
(*this).member = 4;
With a few exceptions relating to name lookup in templates, the names of members refer to the current instances member automatically, as explained in the other answer, so this->
can be dropped, usually:除了一些与模板中的名称查找相关的例外,成员的名称自动引用当前实例成员,如另一个答案中所述,因此可以删除
this->
,通常:
member = 4;
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