学步园

Example 2-18 展示了 traceback 模块允许你在程序里打印异常的跟踪返回 (Traceback)信息, 类似未捕获异常时解释器所做的. 如 Example 2-18 所示.

2.11.0.1. Example 2-18. 使用 traceback 模块打印跟踪返回信息

File: traceback-example-1.py


# note! importing the traceback module messes up the

# exception state, so you better do that here and not

# in the exception handler

# 注意! 导入 traceback 会清理掉异常状态, 所以

# 最好别在异常处理代码中导入该模块

import traceback


try:

    raise SyntaxError, "example"

except:

    traceback.print_exc()

Traceback (innermost last):

  File "traceback-example-1.py", line 7, in ?

SyntaxError: example

Example 2-19 使用 StringIO 模块将跟踪返回信息放在字符串中.

2.11.0.2. Example 2-19. 使用 traceback 模块将跟踪返回信息复制到字符串

File: traceback-example-2.py


import traceback

import StringIO


try:

    raise IOError, "an i/o error occurred"

except:

    fp = StringIO.StringIO()

    traceback.print_exc(file=fp)

    message = fp.getvalue()


    print "failure! the error was:", repr(message)

failure! the error was: 'Traceback (innermost last):/012  File

"traceback-example-2.py", line 5, in ?/012IOError: an i/o error

occurred/012'

你可以使用 extract_tb 函数格式化跟踪返回信息, 得到包含错误信息的列表, 如 Example 2-20 所示.

2.11.0.3. Example 2-20. 使用 traceback Module 模块编码 Traceback 对象

File: traceback-example-3.py


import traceback

import sys


def function():

    raise IOError, "an i/o error occurred"


try:

    function()

except:

    info = sys.exc_info()

    for file, lineno, function, text in traceback.extract_tb(info[2]):

        print file, "line", lineno, "in", function

        print "=>", repr(text)

    print "** %s: %s" % info[:2]

traceback-example-3.py line 8 in ?

=> 'function()'

traceback-example-3.py line 5 in function

=> 'raise IOError, "an i/o error occurred"'

** exceptions.IOError: an i/o error occurred