Python exception handling records

References to come: PythonCookbook

First of all you know, all the abnormal things a class.

If a single block of code to handle all the different anomalies, they can be grouped into one of the tuples.

from urllib.error import URLError

try:
    object.get_url(url)
except (URLError, ValueError, SocketTimeout):
    object.remove_url(url)

 This error Ganso (URLError, ValueError, SocketTimeout) to capture will be executed object.remove_url (url)

 

If a single take a different approach, it can be placed in a separate except

try:
    object.get_url(url)
except (URLError, ValueError):
    object.remove_url(url)
except SocketTimeout:
    object.other_do(url)

 

There are many grouped into the inheritance hierarchy, for such an exception, you can catch all exceptions by specifying a base class.

try:
    f = open('a.txt')
except (FileNotFoundError, PermissionError):
    ...

try:
    f = open('a.txt')
except OSError:
    ...
# Of such investigation under the following sub-categories
print(OSError.__subclasses__())
Print () 
# View table inheritance
print(FileNotFoundError.__mro__)

 

[<class 'ConnectionError'>, <class 'BlockingIOError'>, <class 'ChildProcessError'>, <class 'FileExistsError'>, 
<class 'FileNotFoundError'>, <class 'IsADirectoryError'>, <class 'NotADirectoryError'>, <class 'InterruptedError'>,
 <class 'PermissionError'>, <class 'ProcessLookupError'>, <class 'TimeoutError'>, <class 'io.UnsupportedOperation'>, <class 'signal.ItimerError'>]

(<class 'FileNotFoundError'>, <class 'OSError'>, <class 'Exception'>, <class 'BaseException'>, <class 'object'>)

 The book is not rigorous local things, the type of error is more and more obvious OSError included.

 

We can also as e, the e is captured to the wrong instance, the instance, then they should have a bunch of attributes, you can also view the type of e by type (e) ways to facilitate the accurate capture.

Wherein the error property can capture the error code.

except to execute appropriate exception capture down, except the following will not be executed.

try:
    f = open('a.txt')
except OSError as e:
　　 print(dir(e))
    print('OSError')
    # This certainly will not be executed, should be FileNotFoundError OSError parent class that contains it to all exceptions are captured
except FileNotFoundError:
    print('FileNotFoundError')

At the attributes of objects on the following OSError

['__cause__', '__class__', '__context__', '__delattr__', '__dict__', 
'__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__',
 '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__ne__', '__new__', 
'__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__setstate__', '__sizeof__', '__str__', 
'__subclasshook__', '__suppress_context__', '__traceback__', 'args', 'characters_written', 'errno', 'filename', 'filename2', 'strerror', 'with_traceback']

 

Catch all exceptions

try:
    ...
# General error this enough
except Exception as e:
    ...
# This is the wrong father
except BaseException as e:
    ...

 In addition to SystemExit, KeyboardInterrupt, and GeneratorExit, Exception can capture