Try...Except Advanced

Try...Except Advanced

Many exceptions can be raised together, and there are extra blocks: else and finally.

Raise multiple exceptions

try:
    print(x)
except NameError:
    print("Variable x is not defined")
except:
    print("Something else went wrong")

The first matching except runs.

Raise one exception

You can catch several types in one tuple:

try:
    x = int("not a number")
except (ValueError, TypeError):
    print("Bad value or type")

else

Runs only if NO exception happened:

try:
    print("Hello")
except:
    print("Something went wrong")
else:
    print("Nothing went wrong")

finally

Runs whether or not an exception occurred:

try:
    print(x)
except:
    print("Something went wrong")
finally:
    print("The 'try except' is finished")

Use finally for cleanup, like closing files.

Raise your own exceptions

raise throws an error on purpose:

x = -1
if x < 0:
    raise Exception("Sorry, no numbers below zero")

Custom exception types

class MyError(Exception):
    pass

raise MyError("custom problem")

TL;DR

• Multiple except blocks handle different errors.
• else runs on success; finally always runs.
• raise throws your own errors.
• Custom exceptions subclass Exception.