如何重定向标准错误在Python？通过Python C API？ [英] How to redirect stderr in Python? Via Python C API?

问题描述

这是我的两个问题最近一个组合：结果
[1] <一个href=\"http://stackoverflow.com/questions/1954494/python-instance-method-in-c\">http://stackoverflow.com/questions/1954494/python-instance-method-in-c

[2] <一个href=\"http://stackoverflow.com/questions/1956142/how-to-redirect-stderr-in-python\">http://stackoverflow.com/questions/1956142/how-to-redirect-stderr-in-python

This is a combination of my two recent questions:
[1] http://stackoverflow.com/questions/1954494/python-instance-method-in-c
[2] http://stackoverflow.com/questions/1956142/how-to-redirect-stderr-in-python

我想记录从python脚本标准输出和错误的输出。

I would like to log the output of both stdout and stderr from a python script.

我要问的是，根据创建一个新的类型的东西[1]似乎相当复杂。难道它简化了东西，如果没有必要揭露新型Python的，即它会只在C存在？

The thing I want to ask is, to create a new type according to [1] seems fairly complicated. Does it simplifies the things if there was no need to expose the new type to Python, i.e. it would only exist in C?

我的意思是，当在Python的PyFile_WriteObject打印的东西它去对象/ fileobject.c，并有它检查是否有可能写入它的参数：

I mean, when Python prints something it goes to "Objects/fileobject.c" and there in "PyFile_WriteObject" it check whether it is possible to write to its argument:

writer = PyObject_GetAttrString(f, "write");
if (writer == NULL)
...

另外，还可能得到输出和错误是这样的：

Also, it is possible to get stdout and stderr like this:

PyObject* out = PySys_GetObject("stdout");
PyObject* err = PySys_GetObject("stderr");

我的问题是那么，它在某种程度上可以构造满足上述必要的PyObject'PyObject_GetAttrString（F，写）'，是可调用，所以我可以这样写：

My question is then, is it somehow possible to construct necessary PyObject which satisfies the above 'PyObject_GetAttrString(f, "write")' and is callable so I can write:

PySys_SetObject("stdout", <my writer object / class / type / ?>);

的http://docs.python.org/c-api/sys.html?highlight=pysys%5Fsetobject#PySys%5FSetObject

这样的话，就没有必要暴露新的作家型到Python脚本的其余部分，所以我想这可能是一个有点简单写code ...？

This way, there would be no need to expose the new "writer type" to the rest of Python script so I thought it might be a bit simpler to write the code...?

推荐答案

只是做一个模块对象（你这样做，无论如何，如果你正在使用C API - ！），并使其有一个合适的写功能 - 该模块的对象将是适合作为第二个参数 PySys_SetObject

Just make a module object (you're doing that anyway, if you're using the C API!-) and make it have a suitable write function -- that module object will be suitable as the second argument to PySys_SetObject.

在我回答你的其他问题我指出你 xxmodule.c ，在Python的C程序源代码示例文件，这是有很多例子，包括类型的模块和各种功能 - 你可以从那里即使（神秘地对我）工作，你考虑作出新的类型的一部分太难了 - 。）

In my answer to your other question I pointed you to xxmodule.c, an example file in Python's C sources, which is a module with a lot of examples including types and functions of various kinds -- you can work from there even if (mysteriously to me) you consider the "make a new type" part too difficult;-).

修改：这里有一个简单的工作示例（ aview.py ）

Edit: here's a trivial working example (aview.py):

#include "Python.h"
#include <stdio.h>

static PyObject *
aview_write(PyObject *self, PyObject *args)
{
    const char *what;
    if (!PyArg_ParseTuple(args, "s", &what))
        return NULL;
    printf("==%s==", what);
    return Py_BuildValue("");
}

static PyMethodDef a_methods[] = {
    {"write", aview_write, METH_VARARGS, "Write something."},
    {NULL, NULL, 0, NULL}
};

PyMODINIT_FUNC
initaview(void)
{
    PyObject *m = Py_InitModule("aview", a_methods);
    if (m == NULL) return;
    PySys_SetObject("stdout", m);
}

一旦 aview 模块已正确安装：

$ python
Python 2.5.4 (r254:67917, Dec 23 2008, 14:57:27) 
[GCC 4.0.1 (Apple Computer, Inc. build 5363)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import aview
>>> print 'ciao'
==ciao====
==>>>

...排放标准输出任何字符串中写入 == 周围的迹象（这打印电话 .WRITE 两次：用'侨'，然后用新行再次）

...any string emitted to standard output is written with == signs around it (and this print calls .write twice: with 'ciao', and then again with a newline).

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