Challenge 3 of 3 on Practice Creating and using functions in python challenge

Since you got through Challenge 2 of 3, you understood how to catch errors. The cool thing about Python is that you can catch multiple exception types with the try/except block.

The subtle part is that the challenge calls for you to print out the error message that comes from the Exception class and put it inside in the parenthesis. I am putting the Exception into the variable "e".

This can be done in several ways, but I demonstrate the most basic way to do it.

Good luck on your Python journey!

try:
    tweet(message)
except CommunicationError:
    print("An error occurred attempting to connect to Twitter.  Please try again!")
except MessageTooLongError as e:
    print("Oh no! Your message was too long ({})".format(e))

The Challenge is being used to illustrate intermediate error handling. The print messages are meant for the Challenge grader to read.

The "as err" or "as e" is a way that Python can take an instance of the Exception object class and give it to the user for deeper inspection, printing, or logging. In our case, we simply want the error string to print. That's why we used the .format() method of the string.

Some objects can produce very informative errors, some not so much. The ones that aren't informative have to be handled with more care if we want to have robust programs that won't just die when these encounter a runtime error, but might log or display the error-- allowing the user to correct the error or simply move on.

From the Python documentation:

The except clause may specify a variable after the exception name. The variable is bound to an exception instance with the arguments stored in instance.args. For convenience, the exception instance defines __str__() so the arguments can be printed directly without having to reference .args. One may also instantiate an exception first before raising it and add any attributes to it as desired.

https://docs.python.org/3/tutorial/errors.html

I still don't understand the "as err" or "as e" thing... what's the difference with the CommunicationError message? Why adding parenthesis to the MessageTooLongError message? I am missing something :/

Just documenting that this worked, thanks to Jeff Muday on Dec 13, 2018:

CommunicationError = "An error occurred attempting to connect to Twitter. Please try again!"


message = input("What would you like to tweet?  ")

try: 
    tweet(message) 

except MessageTooLongError as e:
    print("Oh no! Your message was too long ({})".format(e))
except: 
    print(CommunicationError)