在Python中获取异常类名？ [英] getting the exception class name in python?

问题描述

我想在一个异常处理程序中生成一个字符串，其中包含异常的名称，以及传递的任何参数……几乎是使用Traceback获得的最终输出。

I want to generate a string in an exception handler that contains the name of the exception, and any arguments passed...oretty much the final output that one gets with Traceback.

例如，如果调用 raise bar.FnordError（ message），则在异常处理程序中，我想生成字符串： bar.FnordError：消息

For example, if raise bar.FnordError("message") is called, in the exception handler, I want to produce the string: "bar.FnordError: message"

我希望它适用于内置的异常以及当前模块和其他模块中的异常。这是我想出的，但似乎不是很Python。

I want it to work for built in exceptions, as well as exceptions in the current and other modules. This is what I came up with, but it doesn't seem very pythonic.

def this_is_lame(err):
    if type(err).__module__ in ['__main__', 'builtins']:
        return "{}: {}".format(type(err).__name__, err)
    else:
        return "{}.{}: {}".format(type(err).__module__, type(err).__name__, err)

我通过python中的BaseException C代码和Traceback标准库进行了挖掘。我似乎缺少正确的不错的访问器。

I've dug through the BaseException C code in python, and the Traceback standard library. I seem to be missing the correct "nice" accessor.

BaseException .__ format __ 是否记录在任何地方？

Is BaseException.__format__ documented anywhere? Are there escapes for it?

我在翻译中玩过，什么也没给我我想要的东西。

I've played around in the interpreter and nothing quite gives me what I want.

import sys
import traceback

import bar

try:
    raise bar.FnordError("message")
except Exception as err:
    print(type(err))
    print(repr(err))
    print(type(err).__module__)
    print(type(err).__name__)
    print(err)
    print("this is what I want: '{}'".format(this_is_lame(err)))

print()

try:
    raise ValueError("message")
except Exception as err:
    print(type(err))
    print(repr(err))
    print(type(err).__module__)
    print(type(err).__name__)
    print("this is what I want: '{}'".format(this_is_lame(err)))

会产生：

$ python foo.py
<class 'bar.FnordError'>
FnordError('message',)
bar
FnordError
message
this is what I want: 'bar.FnordError: message'

<class 'ValueError'>
ValueError('message',)
builtins
ValueError
this is what I want: 'ValueError: message'

推荐答案

没有不错的访问器。 Python本身所做的事情与您在默认的 sys.excepthook 中所做的非常相似，尽管在 __ main __ 中定义了异常打印为 __ main __。WhateverException 。

There's no "nice" accessor. Python itself does something pretty similar to what you're doing in the default sys.excepthook, although exceptions defined in __main__ print as __main__.WhateverException.

如果您想了解Python本身是如何做到的，在Python 2上，检查发生在 PyErr_Display ，它检查 strcmp（modstr， exceptions）：

If you want to see how Python itself does it, on Python 2, the check happens in PyErr_Display, which checks strcmp(modstr, "exceptions"):

moduleName = PyObject_GetAttrString(exception, "__module__");
if (moduleName == NULL)
    err = PyFile_WriteString("<unknown>", f);
else {
    char* modstr = PyString_AsString(moduleName);
    if (modstr && strcmp(modstr, "exceptions"))
    {
        err = PyFile_WriteString(modstr, f);
        err += PyFile_WriteString(".", f);
    }
    Py_DECREF(moduleName);
}

在Python 3上， print_exception 检查 _PyUnicode_CompareWithId（

On Python 3, print_exception checks _PyUnicode_CompareWithId(moduleName, &PyId_builtins).

moduleName = _PyObject_GetAttrId(type, &PyId___module__);
if (moduleName == NULL || !PyUnicode_Check(moduleName))
{
    Py_XDECREF(moduleName);
    err = PyFile_WriteString("<unknown>", f);
}
else {
    if (_PyUnicode_CompareWithId(moduleName, &PyId_builtins) != 0)
    {
        err = PyFile_WriteObject(moduleName, f, Py_PRINT_RAW);
        err += PyFile_WriteString(".", f);
    }
    Py_DECREF(moduleName);
}

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