python exception message capturing

问题

import ftplib
import urllib2
import os
import logging
logger = logging.getLogger('ftpuploader')
hdlr = logging.FileHandler('ftplog.log')
formatter = logging.Formatter('%(asctime)s %(levelname)s %(message)s')
hdlr.setFormatter(formatter)
logger.addHandler(hdlr)
logger.setLevel(logging.INFO)
FTPADDR = "some ftp address"

def upload_to_ftp(con, filepath):
    try:
        f = open(filepath,'rb')                # file to send
        con.storbinary('STOR '+ filepath, f)         # Send the file
        f.close()                                # Close file and FTP
        logger.info('File successfully uploaded to '+ FTPADDR)
    except, e:
        logger.error('Failed to upload to ftp: '+ str(e))

This doesn't seem to work, I get syntax error, what is the proper way of doing this for logging all kind of exceptions to a file

回答1:

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:
    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:
    logger.error('Failed to upload to ftp: '+ str(e))

回答2:

The syntax is no longer supported in python 3. Use the following instead.

try:
    do_something()
except BaseException as e:
    logger.error('Failed to do something: ' + str(e))

回答3:

Updating this to something simpler for logger (works for both python 2 and 3). You do not need traceback module.

import logging

logger = logging.Logger('catch_all')

def catchEverythingInLog():
    try:
        ... do something ...
    except Exception as e:
        logger.error(e, exc_info=True)
        ... exception handling ...

This is now the old way (though still works):

import sys, traceback

def catchEverything():
    try:
        ... some operation(s) ...
    except:
        exc_type, exc_value, exc_traceback = sys.exc_info()
        ... exception handling ...

exc_value is the error message.

回答4:

There are some cases where you can use the e.message or e.messages.. But it does not work in all cases. Anyway the more safe is to use the str(e)

try:
  ...
except Exception as e:
  print(e.message)

回答5:

You can use logger.exception("msg") for logging exception with traceback:

try:
    #your code
except Exception as e:
    logger.exception('Failed: ' + str(e))

回答6:

If you want the error class, error message and stack trace (or some of those), use sys.exec_info().

Minimal working code with some formatting:

import sys
import traceback

try:
    ans = 1/0
except BaseException as ex:
    # Get current system exception
    ex_type, ex_value, ex_traceback = sys.exc_info()

    # Extract unformatter stack traces as tuples
    trace_back = traceback.extract_tb(ex_traceback)

    # Format stacktrace
    stack_trace = list()

    for trace in trace_back:
        stack_trace.append("File : %s , Line : %d, Func.Name : %s, Message : %s" % (trace[0], trace[1], trace[2], trace[3]))

    print("Exception type : %s " % ex_type.__name__)
    print("Exception message : %s" %ex_value)
    print("Stack trace : %s" %stack_trace)

Which gives the following output:

Exception type : ZeroDivisionError
Exception message : division by zero
Stack trace : ['File : .\\test.py , Line : 5, Func.Name : <module>, Message : ans = 1/0']

sys.exec_info()

This gives you details about the most recent exception. It returns a tuple of (type, value, traceback).

traceback is an instance of traceback object. You can format the trace with the methods provided. More can be found in the traceback documentation .

回答7:

After python 3.6, you can use formatted string literal. It's neat! (https://docs.python.org/3/whatsnew/3.6.html#whatsnew36-pep498)

try
 ...
except Exception as e:
    logger.error(f"Failed to upload to ftp: {e}")

回答8:

You can try specifying the BaseException type explicitly. However, this will only catch derivatives of BaseException. While this includes all implementation-provided exceptions, it is also possibly to raise arbitrary old-style classes.

try:
  do_something()
except BaseException, e:
  logger.error('Failed to do something: ' + str(e))

回答9:

Use str(ex) to print execption

try:
   #your code
except ex:
   print(str(ex))

来源：https://stackoverflow.com/questions/4690600/python-exception-message-capturing

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python

exception

logging

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