[英]How are the contents of the builtins module available in the global namespace without import in Python?
I've been using Python for a good period of time. 我一直在使用Python很长一段时间。 I have never found out how built-in functions work. 我从来没有发现内置函数是如何工作的。 In different words, how are they included without having any module imported to use them? 换句话说,如果没有导入任何模块来使用它们,它们是如何被包含的? What if I want to add to them (locally)? 如果我想添加(本地)怎么办?
This may seem naive. 这可能看起来很幼稚。 But, I haven't really found any answer that explains comprehensively how do we have built-in functions, global variables, etc., available to us when developing a script. 但是,我还没有真正找到任何答案,全面解释我们在开发脚本时如何使用内置函数,全局变量等。
In a nutshell, where do we include the builtins module? 简而言之,我们在哪里包含内置模块?
I have encountered this question . 我遇到过这个问题 。 But it gives a partial answer to my question. 但它给出了我的问题的部分答案。
The not-implementation-details part of the answer is that the builtins
module, or __builtin__
in Python 2, provides access to the built-ins namespace. 答案的非实现细节部分是builtins
模块,或Python 2中的__builtin__
,提供对内置命名空间的访问。 If you want to modify the built-ins (you usually shouldn't), setting attributes on builtins
is how you'd go about it. 如果你想修改内置插件(你通常不应该这样做),在builtins
设置上设置属性是你如何去做的。
The implementation details part of the answer is that Python keeps track of built-ins in multiple ways. 实现细节部分答案是Python以多种方式跟踪内置函数。 For example, each frame object keeps track of the built-in namespace it's using, which may be different from other frames' built-in namespaces. 例如,每个框架对象都会跟踪它正在使用的内置命名空间,这可能与其他框架的内置命名空间不同。 You can access this through a frame's f_builtins
attribute. 您可以通过框架的f_builtins
属性访问它。 When a LOAD_GLOBAL
instruction fails to find a name in the frame's globals, it looks in the frame's builtins. 当LOAD_GLOBAL
指令无法在框架的全局变量中找到名称时,它会查看框架的内部结构。 There's also a __builtins__
global variable in most global namespaces, but it's not directly used for built-in variable lookup; 在大多数全局命名空间中还有一个__builtins__
全局变量,但它并不直接用于内置变量查找; instead, it's used to initialize f_builtins
in certain situations during frame object creation. 相反,它用于在帧对象创建期间在某些情况下初始化f_builtins
。 There's also a builtins
reference in the global PyInterpreterState
, which is used as default builtins if there's no current frame object. 全局PyInterpreterState
还有一个builtins
引用,如果没有当前帧对象,它将用作默认内置函数。
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