如何正确使用 Python 的 C API 和异常? [英] How do I properly use Python's C API and exceptions?

问题描述

如果我做类似的事情

 >>>x = int(1,2,3,4,5)

我立即收到一个致命错误(如果它是在预先编写的脚本中，则会终止程序执行)

 回溯(最近一次调用最后一次):文件<stdin>"，第 1 行，在 <module> 中类型错误:int() 最多接受 2 个参数(给定 5 个)

和 x 保持未定义:

 >>>X回溯(最近一次调用最后一次):文件<stdin>"，第 1 行，在 <module> 中NameError: 名称 'x' 未定义

我将如何在 Python 的 C API 中实现它?我找到了一些文档，但我不确定我是否知道如何正确使用它.

这是我一直在尝试的:

1. 打印:

   if(something) {PyErr_SetString(PyExc_TypeError, "哦不！");PyErr_Print();}

   不幸的是，这只会打印异常并且程序继续.此外，如果我理解正确的话，PyErr_Print() 会从某种队列中删除异常，因此 Python 认为它已被处理.这是它的样子:

   <预><代码>>>>导入真棒模组>>>x = awesomemod.thing()类型错误:哦不！>>>x # x 被定义是因为函数最终返回 None>>>

2. PyErr_Occurred():

   if(something) {PyErr_SetString(PyExc_TypeError, "哦不！");PyErr_Occurred();}

   行为:

   <预><代码>>>>导入真棒模组>>>真棒mod.thing()>>>类型错误:哦不！>>>

   所以它做的有点晚......

3. 返回 PyErr_Occurred():

   if(something) {PyErr_SetString(PyExc_TypeError, "哦不！");返回 PyErr_Occurred();}

   行为:

   <预><代码>>>>导入真棒模组>>>真棒mod.thing()<type 'exceptions.TypeError'>>>>类型错误:哦不！

   这个真的很奇怪.

我需要做什么才能获得内置函数的行为?

我尝试了@user2864740 在评论中建议的内容，效果很好！

 if(something) {PyErr_SetString(PyExc_TypeError, "哦不！");返回(PyObject *)NULL；}

解决方案

在 C 中引发异常是通过设置异常对象或字符串然后从函数返回 NULL 来完成的.

if I do something like

 >>> x = int(1,2,3,4,5)

I immediately get a fatal error (one that would end program execution if it was in a pre-written script)

 Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
 TypeError: int() takes at most 2 arguments (5 given)

and x remains undefined:

 >>> x
 Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
 NameError: name 'x' is not defined

How would I go about implementing that in Python's C API? I found some documentation for it, but I am not sure that I know how to use it correctly.

Here is what I have been trying:

1. Print:

   if(something) {
       PyErr_SetString(PyExc_TypeError, "Oh no!");
       PyErr_Print();
   }
   

   This, unfortunately, only prints the exception and the program continues. Additionally,—if I understand it correctly—PyErr_Print() removes the exception from some sort of queue so Python thinks that it is handled. This is what it looks like:

   >>> import awesomemod
   >>> x = awesomemod.thing()
   TypeError: Oh no!
   >>> x # x is defined because the function returns None eventually
   >>> 
   

2. PyErr_Occurred():

   if(something) {
       PyErr_SetString(PyExc_TypeError, "Oh no!");
       PyErr_Occurred();
   }
   

   Behavior:

   >>> import awesomemod
   >>> awesomemod.thing()
   >>>
   TypeError: Oh no!
   >>>
   

   So it does it kind of late...

3. return PyErr_Occurred():

   if(something) {
       PyErr_SetString(PyExc_TypeError, "Oh no!");
       return PyErr_Occurred();
   }
   

   Behavior:

   >>> import awesomemod
   >>> awesomemod.thing()
   <type 'exceptions.TypeError'>
   >>>
   TypeError: Oh no!
   

   This one is just really weird.

What do I need to do to get the behavior of built-in functions?

Edit: I tried what @user2864740 suggested in a comment and it worked perfectly!

 if(something) {
     PyErr_SetString(PyExc_TypeError, "Oh no!");
     return (PyObject *) NULL;
 }

解决方案

Raising an exception in C is done by setting the exception object or string and then returning NULL from the function.

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