程序出错的时候，我们往往需要根据异常信息来找到具体出错的代码。简单地用print打印异常信息并不能很好地追溯出错的代码：
# -*- coding: utf-8 -*-
def foo(a, b):
c = a + b
raise ValueError('test')
return c
def bar(a):
print('a + 100:', foo(a, 100))
def main():
try:
bar(100)
except Exception as e:
print(repr(e))
if __name__ == '__main__':
main()
输出：
ValueError('test',)
打印的异常信息不够详细，对错误追踪没有多大帮助。这时候异常堆栈信息就派上用场了。下面简单介绍几种打印异常堆栈信息的方法。
1.最简单的方法之一就是使用logging.exception
# -*- coding: utf-8 -*-
import logging
def foo(a, b):
c = a + b
raise ValueError('test')
return c
def bar(a):
print('a + 100:', foo(a, 100))
def main():
try:
bar(100)
except Exception as e:
logging.exception(e)
if __name__ == '__main__':
main()
输出：
ERROR:root:test
Traceback (most recent call last):
File "E:/git_work/scrapy_ppt/test.py", line 16, in main
bar(100)
File "E:/git_work/scrapy_ppt/test.py", line 11, in bar
print('a + 100:', foo(a, 100))
File "E:/git_work/scrapy_ppt/test.py", line 6, in foo
raise ValueError('test')
ValueError: test
从异常堆栈信息中我们可以不费力气就找出错误代码是哪一行。
2.其它方法：
# -*- coding: utf-8 -*-
import traceback
import sys
def foo(a, b):
c = a + b
raise ValueError('test')
return c
def bar(a):
print('a + 100:', foo(a, 100))
def main():
try:
bar(100)
except Exception as e:
# 方法二
traceback.print_exc()
# 方法三
msg = traceback.format_exc()
print(msg)
et, ev, tb = sys.exc_info()
# 方法四
traceback.print_tb(tb)
# 方法五
traceback.print_exception(et, ev, tb)
# 方法六
msg = traceback.format_exception(et, ev, tb)
for m in msg:
print(m)
if __name__ == '__main__':
main()