How to use an error handling function on another function?

Question

I have a script, main.py, that runs a few functions from other scripts in the directory. I had the very unoriginal idea to send myself Slack notifications if specific functions ran correctly or failed, i.e. error handling. How would I use an error handling function located in a separate script - call the file slack_notifications.py - in my main.py script? This linked question starts to get at the answer, but it doesn't get to the calling the error function from somewhere else.

main.py script:

import scraper_file
import slack_notifications

# picture scrape variable
scrape_object = 'Barack Obama'

# scraper function called 
scraped_image = scraper_file.pic_scrape(scrape_object)

# error handling?
slack_notifications.scrape_status(scrape_object)

I have tried embedding the called scraper function into the scrape_status() function, like this: scraped_image = (slack_notifications.scrape_status(scraper_file.pic_scrape(scrape_object))) and a few other ways, but that doesn't really tell you if it ran successfully, right?

slack_notifications.py script:


testing = "dunderhead"

def scrape_status(x):

    # if this function gets a positive return from the scrape function
    # if this function gets any error from the scrape function
    try:
        x
        print(x + ' worked!')
    except:
        print(x + ' failed!')

if __name__ == '__main__':
    scrape_status(testing)

Is there a way to do this? I have been going off these instructions, too.

your scrape_status seems totally useless. It will run try/except too late - after error hapends - so it can't catch it. You would have to rather send function's name (without () ) into scrape_status and use it with () to execute it inside try/except - and then it can catch it. OR simply you have to run scraper_file.pic_scrape(scrape_object) inside try/except and it would be simpler if you use try/except directly inside scraper_file.pic_scrape(scrape_object) instead of creating universal function scrape_Status() for this — furas
– furas, Commented Apr 1, 2021 at 18:02
code in yoiur first works because function input() was moved from outside error_handler into inside error_handler and you would have to do the same with scraper_file.pic_scrape(scrape_object) - you have to move it into scrape_status but you can't do this using scraper_file.pic_scrape(scrape_object) because it runs it outside scrape_status. All your idea is overcomplicated. Better put all code in one file and don't try to create universal function scrape_status — furas
– furas, Commented Apr 1, 2021 at 18:06

furas · Accepted Answer · 2021-04-01 18:49:07Z

1

Code in your first link works because function input() was moved from outside error_handler() into inside error_handler() and it is executed inside `try/except.

Your code always runs function outside error handler scrape_status() and it sends only result from executed function - so it never runs it inside try/except.

You would have to send separatelly function's name (without () and arguments) and separatelly arguments - and then it can run it inside try/except

def scrape_status(function, *args):
    try:
        function(*args)
        print(function.__name__ + ' worked!')
    except:
        print(function.__name__ + ' failed!')

But it means you have to send function as

scrape_status(scraper_file.pic_scrape, scrape_object)

instead of

scrape_status( scraper_file.pic_scrape(scrape_object) )

and this is not readable - so I don't know if it is good idea to create universal error handler.

Minimal working example

def scrape_status(function, *args, **kwargs):
    try:
        result = function(*args, **kwargs)  # some functions may return result
        print(function.__name__ + ' worked!')
        return result
    except:
        print(function.__name__ + ' failed!')

# ----

# this function needs `arg1, arg2` to work correctly
def testing(arg1, arg2):
    print(arg1, arg2)

# --- main ---
    
print('--- test 1 ---')    
# send funciton's name `testing` and argument(s) `'hello', 'world'`   
scrape_status(testing, 'hello', 'world')  # OK

print('--- test 2 ---')    
# send funciton's name `testing` without argument(s) 
scrape_status(testing)  # ERROR

Result:

--- test 1 ---
hello world
testing worked!
--- test 2 ---
testing failed!

EDIT:

I created new example using decorator based on answers in question General decorator to wrap try except in python?. Now code use readableand it needs to use decorator @scrape_status('') only when function is defined

@scrape_status('')
def testing(arg1, arg2):
    print(arg1, arg2)

Minimal working code:

def scrape_status():
  def decorate(function):
    def applicator(*args, **kwargs):
      try:
         result = function(*args, **kwargs)
         print(function.__name__ + ' worked!')
         return result
      except:
         print(function.__name__ + ' failed!')

    return applicator

  return decorate

# ----

# this function needs `arg1, arg2` to work correctly
@scrape_status()
def testing(arg1, arg2):
    print(arg1, arg2)

# --- main ---
  
print('--- test 1 ---')    
# send function's name `testing` and argument(s) `'hello', 'world'`   
testing('hello', 'world')  # OK

print('--- test 2 ---')    
# send function's name `testing` without argument(s) 
testing()  # ERROR

As I remeber there could be some module(s) with more complex decorators - ie. one decorator could repeate function 3 times if it was raising error. It could be uses to repeate question in input() if answer was wrong, or repeate downloading file if there was problem to download it.

edited Apr 1, 2021 at 18:49

answered Apr 1, 2021 at 18:22

furas

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3 Comments

papelr Over a year ago

Gotcha - I agree, does look totally useless. Will try this out after work!

furas Over a year ago

maybe it could be more readable with some decorator like in answers for General decorator to wrap try except in python?. Or maybe there is module for this

furas Over a year ago

I created code using decorator from question ` General decorator to wrap try except in python?.` and now code is nice and readable.

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