Python 的异常处理

参考链接：https://blog.youkuaiyun.com/lengxingxing_/article/details/56317838

https://segmentfault.com/a/1190000012625548

一、利用traceback模块手自定义处理异常

1、第一种解析方式

'''1 第一种解析方式'''
def f():
    1 / 0
try:
    f()
except:
    a, b, c = sys.exc_info()
    print(a, b, c)
    for filename, linenum, funcname, source in traceback.extract_tb(c):
        print(filename, linenum, funcname, source)

输出结果为

<class 'ZeroDivisionError'> division by zero <traceback object at 0x7f3688e96c48>
/home/duxin/surfing/surfing_code/python-cron/sf_crontab/test/python异常和上下文协议/python_exception.py 12 <module> f()
/home/duxin/surfing/surfing_code/python-cron/sf_crontab/test/python异常和上下文协议/python_exception.py 7 f 1 / 0

2、第二种解析方式

'''2 第二中解析方式'''
try:
    f()
except:
    a, b, c = sys.exc_info()
    print(a, b, c)
    print(traceback.print_exception(a, b, c))

输出结果：

Traceback (most recent call last):
<class 'ZeroDivisionError'> division by zero <traceback object at 0x7fc5a6652d08>

None
  File "/home/duxin/surfing/surfing_code/python-cron/sf_crontab/test/python异常和上下文协议/python_exception.py", line 32, in <module>
    f()
  File "/home/duxin/surfing/surfing_code/python-cron/sf_crontab/test/python异常和上下文协议/python_exception.py", line 7, in f
    1 / 0
ZeroDivisionError: division by zero

3、第三种解析

'''3、 cgitb的使用'''
cgitb.enable(context=3, format='text')  # 可以定义异常文件的的保存位置、保存文件的类型
f()

cgitb的两个方法

cgitb.encable(display=1, logdir=None, context=5, format="html")

display 1，发送至浏览器；0， 不发送 
logdir 如果有的话，写到该目录下
context 显示错误代码周围的代码行数
format 是否显示为HTML，除了'html'之外的所有值，都会显示为纯文本

cgitb.handle(info=None)

如果你想用cgitb处理异常，你可以调用这个函数。
info 应当是含有异常类型、异常值和traceback对象的三元组，——如同sys.exc_info()返回的那样。如果不提供info，则从sys.exc_info中获取。

输出结果：

ZeroDivisionError
Python 3.6.7: /usr/bin/python3.6
Sun Apr 28 11:50:09 2019

A problem occurred in a Python script.  Here is the sequence of
function calls leading up to the error, in the order they occurred.

 /home/duxin/surfing/surfing_code/python-cron/sf_crontab/test/python异常和上下文协议/python_exception.py in <module>()
   49 cgitb.enable(context=3, format='text')  # 可以定义异常文件的的保存位置、保存文件的类型
   50 f()
   51 
f = <function f>

 /home/duxin/surfing/surfing_code/python-cron/sf_crontab/test/python异常和上下文协议/python_exception.py in f()
    6 def f():
    7     1 / 0
    8 

ZeroDivisionError: division by zero
    __cause__ = None
    __class__ = <class 'ZeroDivisionError'>
    __context__ = None
    __delattr__ = <method-wrapper '__delattr__' of ZeroDivisionError object>
    __dict__ = {}
    __dir__ = <built-in method __dir__ of ZeroDivisionError object>
    __doc__ = 'Second argument to a division or modulo operation was zero.'
    __eq__ = <method-wrapper '__eq__' of ZeroDivisionError object>
    __format__ = <built-in method __format__ of ZeroDivisionError object>
    __ge__ = <method-wrapper '__ge__' of ZeroDivisionError object>
    __getattribute__ = <method-wrapper '__getattribute__' of ZeroDivisionError object>
    __gt__ = <method-wrapper '__gt__' of ZeroDivisionError object>
    __hash__ = <method-wrapper '__hash__' of ZeroDivisionError object>
    __init__ = <method-wrapper '__init__' of ZeroDivisionError object>
    __init_subclass__ = <built-in method __init_subclass__ of type object>
    __le__ = <method-wrapper '__le__' of ZeroDivisionError object>
    __lt__ = <method-wrapper '__lt__' of ZeroDivisionError object>
    __ne__ = <method-wrapper '__ne__' of ZeroDivisionError object>
    __new__ = <built-in method __new__ of type object>
    __reduce__ = <built-in method __reduce__ of ZeroDivisionError object>
    __reduce_ex__ = <built-in method __reduce_ex__ of ZeroDivisionError object>
    __repr__ = <method-wrapper '__repr__' of ZeroDivisionError object>
    __setattr__ = <method-wrapper '__setattr__' of ZeroDivisionError object>
    __setstate__ = <built-in method __setstate__ of ZeroDivisionError object>
    __sizeof__ = <built-in method __sizeof__ of ZeroDivisionError object>
    __str__ = <method-wrapper '__str__' of ZeroDivisionError object>
    __subclasshook__ = <built-in method __subclasshook__ of type object>
    __suppress_context__ = False
    __traceback__ = <traceback object>
    args = ('division by zero',)
    with_traceback = <built-in method with_traceback of ZeroDivisionError object>

The above is a description of an error in a Python program.  Here is
the original traceback:

Traceback (most recent call last):
  File "/home/duxin/surfing/surfing_code/python-cron/sf_crontab/test/python异常和上下文协议/python_exception.py", line 50, in <module>
    f()
  File "/home/duxin/surfing/surfing_code/python-cron/sf_crontab/test/python异常和上下文协议/python_exception.py", line 7, in f
    1 / 0
ZeroDivisionError: division by zero

4、自定义异常处理

def my_exception_handler(exc_type, exc_value, exc_tb):
    print("i caught the exception:", exc_type, exc_value)
    while exc_tb:
        print("the line no:", exc_tb.tb_lineno)
        print("the frame locals:", exc_tb.tb_frame.f_locals)
        exc_tb = exc_tb.tb_next


sys.excepthook = my_exception_handler
f()

输出结果

i caught the exception: <class 'ZeroDivisionError'> division by zero
the line no: 141
the frame locals: {'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': <_frozen_importlib_external.SourceFileLoader object at 0x7f75cb346278>, '__spec__': None, '__annotations__': {}, '__builtins__': <module 'builtins' (built-in)>, '__file__': '/home/duxin/surfing/surfing_code/python-cron/sf_crontab/test/python异常和上下文协议/python_exception.py', '__cached__': None, 'cgitb': <module 'cgitb' from '/usr/lib/python3.6/cgitb.py'>, 'sys': <module 'sys' (built-in)>, 'traceback': <module 'traceback' from '/usr/lib/python3.6/traceback.py'>, 'f': <function f at 0x7f75cb36cea0>, 'a': <class 'ZeroDivisionError'>, 'b': ZeroDivisionError('division by zero',), 'c': <traceback object at 0x7f75c918b5c8>, 'my_exception_handler': <function my_exception_handler at 0x7f75c9198ea0>}
the line no: 7
the frame locals: {}

当有变量时，the frame locals: {} 的大括号中会以 变量名：变量值 的方式显示出来