Creating Function to handle exceptions in Python

Question

I was wondering if it's possible to write a function to avoid calling a try ... except block each time for risky functions in Python.

I tried following code but it didn't work:

def e(methodtoRun):
    try:
        methodtoRun.call()
    except Exception as inst:
        print(type(inst))    # the exception instance
        print(inst.args)     # arguments stored in .args
        print(inst)          # __str__ allows args to be printed directly,


def divider(a, b):
    return a / b

e(divider(1,0))

In this code, Python runs divider(1,0) and tries to pass result as an argument to the e function.

What I wanted to do is to pass a function as an argument and run it in the function try ... except block so that, if any error occurs, I will add the error to a log directly.

Is this possible?

Answer 1

You can do this .. but it does make code not really better to read.

Your example does not work, because you feed the "result" of the function-call divider(1,0) to e . It never comes to handling the exception because you already called the function and the exception already happened.

You need to pass the function itself and any params to e .

Change it to:

def e(methodtoRun, *args):
    try:
        methodtoRun(*args)    # pass arguments along
    except Exception as inst:
        print(type(inst))    # the exception instance
        print(inst.args)     # arguments stored in .args
        print(inst)          # __str__ allows args to be printed directly,


def divider(a, b):
    return a / b

e(divider,1,0)    # give it the function and any params it needs

To get:

<type 'exceptions.ZeroDivisionError'>
('integer division or modulo by zero',)
integer division or modulo by zero

---

In any serious code review you should get your code back to fix this though. I strongly recommend to not do this - you are only capturing the most general exception and making this construct more flexible will make it horrible to use!

Exceptions should be:

• handled as locally as possible
• as specific as possible

your code is doing the exact opposit.

Doku:

• Exception handling - you copied from there, ref is for others
• arbitraty argument lists aka *args
• unpacking lists