什么是co_names？ [英] What is co_names?

问题描述

说明，价格为 co_names 读取：

局部变量名称元组

但是实际上， co_names 是一个全局变量名的元组，而 co_varnames 是局部变量名称（和参数名称）的元组。例如：

  a = 1 
 
 def f（b）：
c = a + b 
 
 print（f .__ code __。co_varnames）＃打印（'b'，'c'）
 print（f .__ code __。co_names）＃打印（'a'，）
  

此外，文档中的 dis 模块很多指令说明暗示 co_names 包含全局变量的名称。例如， LOAD_GLOBAL description 读取：

将全局名为co_names [namei]加载到堆栈中。

我在这里误解了吗？ co_names 是否真的包含局部变量名称？

编辑07/17/2017

如评论/答案中所述，这似乎是文档错误。已在此处提交了问题。

编辑07/22/2017

提出请求，以解决此文档错误，已批准并等待合并。

解决方案

正如其他人所说的那样，这似乎是文档错误。 关于代码对象的文档显然与 检查 的文档：

co_varnames 是包含局部变量名称的元组（以参数名称开头）； [...] co_names 是一个包含字节码使用的名称的元组;

此外，访问代码对象的属性 co_names 和 co_varnames 与以下内容冲突在检查中表示：

 >> def f（）：
 ... a = 1 
 ... b = 2 
 ... 
> f .__ code __。co_names 
（）
>>> f .__ code __。co_varnames 
（'a'，'b'）
  

此外，评论在 CPython的编译器的源代码中，明确提到 co_varnames 用于局部变量：

  PyObject * u_names; / *所有名称* / 
 PyObject * u_varnames; / *局部变量* / 
  

看不到的原因 co_varnames 是因为上面的代码正在初始化Python用于编译代码的编译器对象的属性。 u_names 和 u_varnames 稍后都传递给 PyCode_New -CPython代码对象的构造函数：

  names = dict_keys_inorder（c-> u-> u_names，0）; 
 varnames = dict_keys_inorder（c-> u-> u_varnames，0）; 
 
 ... 
 
 co = PyCode_New（...，names，varnames，...）; 
  

和 PyCode_New 分配名称和 varnames 分别添加到 co_names 和 co_varnames 属性：

  Py_INCREF（名称）; 
 co-> co_names =名称； 
 Py_INCREF（varnames）; 
 co-> co_varnames = varnames; 
  

---

如果您还没有的话，建议填写 bugs.python.org 上的错误报告，以使Python开发团队知道文档中的这种不一致之处。 / p>

The description for co_names in the inspect module reads:

tuple of names of local variables

However in practice it appears that co_names is a tuple of global variable names while co_varnames is a tuple of local variable names (and argument names). For example:

a = 1

def f(b):
    c = a + b

print(f.__code__.co_varnames)  # prints ('b', 'c')
print(f.__code__.co_names)     # prints ('a',)

Furthermore in the docs for the dis module many instruction descriptions imply that co_names contains names of global variables. For example the LOAD_GLOBAL description reads:

Loads the global named co_names[namei] onto the stack.

Am I misunderstanding something here? Does co_names really contain "names of local variables"?

Edit 07/17/2017

As mentioned in the comments/answers this appears to be a documentation error. Bug issue filed here.

Edit 07/22/2017

Pull request to fix this documentation error approved and waiting to be merged.

解决方案

As other's have already said, this seems to be a documentation error. The documentation for code objects clearly contradicts the documentation for inspect:

co_varnames is a tuple containing the names of the local variables (starting with the argument names); [...] co_names is a tuple containing the names used by the bytecode;

Also, accessing the attributes co_names and co_varnames of code objects conflicts with what was stated in inspect:

>>> def f():
...     a = 1
...     b = 2
... 
>>> f.__code__.co_names
()
>>> f.__code__.co_varnames
('a', 'b')

Furthermore, comments in the source code for CPython's compiler explicitly mention that co_varnames is for local variables:

PyObject *u_names;     /* all names */
PyObject *u_varnames; /* local variables */

The reason you don't see co_varnames is because the above code is initializing attributes for the compiler object that Python uses to compile code. u_names and u_varnames are both later passed into PyCode_New - the constructor for CPython code objects:

names = dict_keys_inorder(c->u->u_names, 0);
varnames = dict_keys_inorder(c->u->u_varnames, 0);

...

co = PyCode_New(..., names, varnames, ... );

And PyCode_New assigns names and varnames to the co_names and co_varnames attributes respectively:

Py_INCREF(names);
co->co_names = names;
Py_INCREF(varnames);
co->co_varnames = varnames;

---

If you already have not, I suggest filling out a bug report at bugs.python.org to let the Python development team know about this inconsistency in the documentation.

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