Catch any error in Python

Question:

Is it possible to catch any error in Python? I don’t care what the specific exceptions will be, because all of them will have the same fallback.

Asked By: user825286

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Source

Answers:

Using except by itself will catch any exception short of a segfault.

try:
    something()
except:
    fallback()

You might want to handle KeyboardInterrupt separately in case you need to use it to exit your script:

try:
    something()
except KeyboardInterrupt:
    return
except:
    fallback()

There’s a nice list of basic exceptions you can catch here. I also quite like the traceback module for retrieving a call stack from the exception. Try traceback.format_exc() or traceback.print_exc() in an exception handler.

Answered By: lunixbochs
try:
    # do something
except Exception, e:
    # handle it

For Python 3.x:

try:
    # do something
except Exception as e:
    # handle it
Answered By: Tjekkles

You might want also to look at sys.excepthook:

When an exception is raised and uncaught, the interpreter calls
sys.excepthook with three arguments, the exception class, exception
instance, and a traceback object. In an interactive session this
happens just before control is returned to the prompt; in a Python
program this happens just before the program exits. The handling of
such top-level exceptions can be customized by assigning another
three-argument function to sys.excepthook.

Example:

def except_hook(type, value, tback):
    # manage unhandled exception here
    sys.__excepthook__(type, value, tback) # then call the default handler

sys.excepthook = except_hook
Answered By: warvariuc

The following only worked for me (both in PY2 and PY3):

try:
  # (Anything that produces any kind of error)
except:
  ertype = sys.exc_info()[0]  # E.g. <class 'PermissionError'>
  description = sys.exc_info()[1]   # E.g. [Errno 13] Permission denied: ...
  # (Handle as needed )
Answered By: Apostolos

Quoting the bounty text:

I want to be able to capture ANY exception even weird ones like
keyboard interrupt or even system exit (e.g. if my HPC manger throws
an error) and get a handle to the exception object e, whatever it
might be. I want to process e and custom print it or even send it by
email

Look at the exception hierarchy, you need to catch BaseException:

BaseException
 +-- SystemExit
 +-- KeyboardInterrupt
 +-- GeneratorExit
 +-- Exception

This will capture KeyboardInterrupt, SystemExit, and GeneratorExit, which all inherit from BaseException but not from Exception, e.g.

try:
    raise SystemExit
except BaseException as e:
    print(e.with_traceback)
Answered By: Chris_Rands

Not mentioning the type of exception you want to handle itself does the job.

Try this:

try:
   #code in which you expect an exception 
except:
   #prints the exception occured

if you want to know the type of exception that occurred:

try:
   # code in which you expect an exception 
except Exception as e:
   print(e)
   # for any exception to be catched
   print(type(e))
   # to know the type of exception.

for detailed explanation go trough this
https://www.tutorialspoint.com/python/python_exceptions.htm

Answered By: gilf0yle
# in python 3

# if you want the error
try:
    func()
except Exception as e:
    exceptionFunc(e)

# if you simply want to know an error occurs
try:
    func()
except:
    exceptionFunc()

# if you don't even wanna do anything
try:
    func()
except:
    pass
Answered By: kennysliding

Built-In Exceptions in Python

Built-In exception classes are divided into Base error classes from which the error classes are defined and Concrete error classes which define exceptions which you are more likely to see time to time.

The more detailed document about the buit-In exception can be found in [https://docs.python.org/3/library/exceptions.html]

Custom Exceptions

It is used to fit your specific application situation. For example, you can create your own exception as RecipeNotValidError as the recipe is not valid in your class for developing a cooking app.

Implementation


class RecipeNotValidError(Exception):    
    def __init__(self):       
        self.message = "Your recipe is not valid"        
        try:            
            raise RecipeNotValidError
        except RecipeNotValidError as e:            
            print(e.message)

These are custom exceptions that are not defined in the standard library. The steps you can follow to create custom classes are :

  1. Subclass the Exception class.
  2. Create a new Exception class of your choice.
  3. Write your code and use the try…except flow to capture and handle your custom exception.
Answered By: DKT