Python exception module traceback usage example analysis

This article example describes the Python exception module traceback usage. Shared for your reference, as follows:

The traceback module is used to trace the return information of an exception. The following example shows this.

import traceback
try:
  raise SyntaxError, "traceback test"
except:
  traceback.print_exc()

will output something like this on the console:

Traceback (most recent call last):
  File "H:", line 3, in <module>
    raise SyntaxError, "traceback test"
SyntaxError: traceback test

Similar to what the interpreter returns when you don't catch an exception.

You can also pass in a file and write the return information to the file, as follows.

import traceback
import StringIO
try:
  raise SyntaxError, "traceback test"
except:
  fp = ()  # Create in-memory file objects
  traceback.print_exc(file=fp)
  message = ()
  print message

The output on the console is the same as in the above example, and the traceback module also provides theextract_tbfunction to format the trace return information to get a list of error messages, as follows.

import traceback
import sys
def tracebacktest():
  raise SyntaxError, "traceback test"
try:
  tracebacktest()
except:
  info = sys.exc_info()
  for file, lineno, function, text in traceback.extract_tb(info[2]):
    print file, "line:", lineno, "in", function
    print text
  print "** %s: %s" % info[:2]

The console output is as follows.

H: line: 7 in <module>
tracebacktest()
H: line: 5 in tracebacktest
raise SyntaxError, "traceback test"
** <type ''>: traceback test

in which the system exit is called when the denominator is 0. The code is as follows.

#!/usr/bin/python
import sys
def division(a=1, b=1):
  if b==0:
     print 'b eq 0'
     (1)
  else:
     return a/b

in, withtry..exceptCatch the exception and thentraceback.print_exc()Print.

The code is as follows.

#!/usr/bin/python
import sys
import traceback
import test1
a=10
b=0
try:
  print (a,b)
except:
  print 'invoking division failed.'
  traceback.print_exc()
  (1)

Failed execution throws an exception.

$python

execution python-2.5.1/python (enodeb/linux)
b eq 0
invoking division failed.
Traceback (most recent call last):
 File "", line 10, in <module>
  (a,b)
 File "/home/fesu/", line 6, in division
  (1)
SystemExit: 1

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I hope that what I have said in this article will help you in Python programming.