How to Get Python Exception Text

Getting the exception value in Python

use str

try:
    some_method()
except Exception as e:
    s = str(e)

Also, most exception classes will have an args attribute. Often, args[0] will be an error message.

It should be noted that just using str will return an empty string if there's no error message whereas using repr as pyfunc recommends will at least display the class of the exception. My take is that if you're printing it out, it's for an end user that doesn't care what the class is and just wants an error message.

It really depends on the class of exception that you are dealing with and how it is instantiated. Did you have something in particular in mind?

python exception message capturing

You have to define which type of exception you want to catch. So write except Exception, e: instead of except, e: for a general exception (that will be logged anyway).

Other possibility is to write your whole try/except code this way:

try:
    with open(filepath,'rb') as f:
        con.storbinary('STOR '+ filepath, f)
    logger.info('File successfully uploaded to '+ FTPADDR)
except Exception, e: # work on python 2.x
    logger.error('Failed to upload to ftp: '+ str(e))

in Python 3.x and modern versions of Python 2.x use except Exception as e instead of except Exception, e:

try:
    with open(filepath,'rb') as f:
        con.storbinary('STOR '+ filepath, f)
    logger.info('File successfully uploaded to '+ FTPADDR)
except Exception as e: # work on python 3.x
    logger.error('Failed to upload to ftp: '+ str(e))

How to get exception message in Python properly

If you look at the documentation for the built-in errors, you'll see that most Exception classes assign their first argument as a message attribute. Not all of them do though.

Notably,EnvironmentError (with subclasses IOError and OSError) has a first argument of errno, second of strerror. There is no message... strerror is roughly analogous to what would normally be a message.

More generally, subclasses of Exception can do whatever they want. They may or may not have a message attribute. Future built-in Exceptions may not have a message attribute. Any Exception subclass imported from third-party libraries or user code may not have a message attribute.

I think the proper way of handling this is to identify the specific Exception subclasses you want to catch, and then catch only those instead of everything with an except Exception, then utilize whatever attributes that specific subclass defines however you want.

If you must print something, I think that printing the caught Exception itself is most likely to do what you want, whether it has a message attribute or not.

You could also check for the message attribute if you wanted, like this, but I wouldn't really suggest it as it just seems messy:

try:
    pass
except Exception as e:
    # Just print(e) is cleaner and more likely what you want,
    # but if you insist on printing message specifically whenever possible...
    if hasattr(e, 'message'):
        print(e.message)
    else:
        print(e)

How do I print an exception in Python?

For Python 2.6 and later and Python 3.x:

except Exception as e: print(e)

For Python 2.5 and earlier, use:

except Exception,e: print str(e)

How to get Python exception text

Well, I found out how to do it.

Without boost (only error message, because code to extract info from traceback is too heavy to post it here):

PyObject *ptype, *pvalue, *ptraceback;
PyErr_Fetch(&ptype, &pvalue, &ptraceback);
//pvalue contains error message
//ptraceback contains stack snapshot and many other information
//(see python traceback structure)

//Get error message
char *pStrErrorMessage = PyString_AsString(pvalue);

And BOOST version

try{
//some code that throws an error
}catch(error_already_set &){

    PyObject *ptype, *pvalue, *ptraceback;
    PyErr_Fetch(&ptype, &pvalue, &ptraceback);

    handle<> hType(ptype);
    object extype(hType);
    handle<> hTraceback(ptraceback);
    object traceback(hTraceback);

    //Extract error message
    string strErrorMessage = extract<string>(pvalue);

    //Extract line number (top entry of call stack)
    // if you want to extract another levels of call stack
    // also process traceback.attr("tb_next") recurently
    long lineno = extract<long> (traceback.attr("tb_lineno"));
    string filename = extract<string>(traceback.attr("tb_frame").attr("f_code").attr("co_filename"));
    string funcname = extract<string>(traceback.attr("tb_frame").attr("f_code").attr("co_name"));
... //cleanup here

Get exception description and stack trace which caused an exception, all as a string

See the traceback module, specifically the format_exc() function. Here.

import traceback

try:
    raise ValueError
except ValueError:
    tb = traceback.format_exc()
else:
    tb = "No error"
finally:
    print tb

How to catch an exception message in python?

Try this:

except Exception as e:
    print(str(e))

Convert exception error to string

From the docs for print()

All non-keyword arguments are converted to strings like str() does and written to the stream

So in the first case, your error is converted to a string by the print built-in, whereas no such conversion takes place when you just try and concatenate your error to a string. So, to replicate the behavior of passing the message and the error as separate arguments, you must convert your error to a string with str().

How to catch python exception and save traceback text as string

The correct function for tb.something(e) is

''.join(tb.format_exception(None, e, e.__traceback__))

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