大家在開發的過程中可能時常碰到一個需求，需要把Python的異常信息輸出到日志文件中。
網上的辦法都不太實用，下面介紹一種實用的，從Python 2.7源碼中扣出來的。
廢話不說 直接上代碼，代碼不多，注釋比較多而已。

import sys, tracebacktraceback_template = '''Traceback (most recent call last): File "%(filename)s", line %(lineno)s, in %(name)s%(type)s: %(message)s/n''' # Skipping the "actual line" item# Also note: we don't walk all the way through the frame stack in this example# see hg.python.org/cpython/file/8dffb76faacc/Lib/traceback.py#l280# (Imagine if the 1/0, below, were replaced by a call to test() which did 1/0.)try:  1/0except:  # http://docs.python.org/2/library/sys.html#sys.exc_info  exc_type, exc_value, exc_traceback = sys.exc_info() # most recent (if any) by default  '''  Reason this _can_ be bad: If an (unhandled) exception happens AFTER this,  or if we do not delete the labels on (not much) older versions of Py, the  reference we created can linger.  traceback.format_exc/print_exc do this very thing, BUT note this creates a  temp scope within the function.  '''  traceback_details = {             'filename': exc_traceback.tb_frame.f_code.co_filename,             'lineno' : exc_traceback.tb_lineno,             'name'  : exc_traceback.tb_frame.f_code.co_name,             'type'  : exc_type.__name__,             'message' : exc_value.message, # or see traceback._some_str()            }  del(exc_type, exc_value, exc_traceback) # So we don't leave our local labels/objects dangling  # This still isn't "completely safe", though!  # "Best (recommended) practice: replace all exc_type, exc_value, exc_traceback  # with sys.exc_info()[0], sys.exc_info()[1], sys.exc_info()[2]  ## 修改這里就可以把traceback打到任意地方，或者存儲到文件中了  print traceback_template % traceback_details