How to get exception message in Python properly

Question

What is the best way to get exceptions  messages from components of standard library in Python   I noticed that in some cases you can get it via message field like this   try    pass except Exception as ex    print ex message    but in some cases  for example  in case of socket errors  you have to do something like this   try    pass except socket error as ex    print ex    I wondered is there any standard way to cover most of these situations

User · Answer

To improve on the answer provided by  artofwarfare  here is what I consider a neater way to check for the message attribute and print it or print the Exception object as a fallback   try      pass  except Exception as e      print getattr e   message   repr e     The call to repr is optional  but I find it necessary in some use cases     Update  1   Following the comment by  MadPhysicist  here s a proof of why the call to repr might be necessary  Try running the following code in your interpreter   try      raise Exception  except Exception as e      print getattr e   message   repr e        print getattr e   message   str e        Update  2   Here is a demo with specifics for Python 2 7 and 3 5  https   gist github com takwas 3b7a6edddef783f2abddffda1439f533

User · Answer

I had the same problem  I think the best solution is to use log exception  which will automatically print out stack trace and error message  such as   try      pass     log info  Success   except      log exception  Failed

User · Answer

If you look at the documentation for the built-in errors  you ll see that most Exception classes assign their first argument as a message attribute  Not all of them do though   Notably EnvironmentError  with subclasses IOError and OSError  has a first argument of errno  second of strerror  There is no message    strerror is roughly analogous to what would normally be a message   More generally  subclasses of Exception can do whatever they want  They may or may not have a message attribute  Future built-in Exceptions may not have a message attribute  Any Exception subclass imported from third-party libraries or user code may not have a message attribute   I think the proper way of handling this is to identify the specific Exception subclasses you want to catch  and then catch only those instead of everything with an except Exception  then utilize whatever attributes that specific subclass defines however you want   If you must print something  I think that printing the caught Exception itself is most likely to do what you want  whether it has a message attribute or not   You could also check for the message attribute if you wanted  like this  but I wouldn t really suggest it as it just seems messy   try      pass except Exception as e        Just print e  is cleaner and more likely what you want        but if you insist on printing message specifically whenever possible        if hasattr e   message            print e message      else          print e

User · Answer

I too had the same problem  Digging into this I found that the Exception class has an args attribute  which captures the arguments that were used to create the exception  If you narrow the exceptions that except will catch to a subset  you should be able to determine how they were constructed  and thus which argument contains the message  try       do something that may raise an AuthException except AuthException as ex     if ex args 0      quot Authentication Timeout  quot           handle timeout    else          generic handling

User · Answer

from traceback import format exc   try      fault   10 0 except ZeroDivision      print format exc     Another possibility is to use the format exc   method from the traceback module

[python] How to get exception message in Python properly

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