python exceptions

except

General format:
try:
    a = 10 / 0
except ZeroDivisionError as err:
    print("Error " + str(err))
else:
    print("It's ok...")  # Else is executed if try statement passes without exception
finally:  # Finally is executed either way

    print("Finalizing")

Python 3.X catching an exception named Exception ignores exceptions related to system exits.

raise

Assert is mostly intended for trapping user-defined constraints, because Python traps programming errors itself,

Assertion example:

def f(x):

    assert x < 0, 'x must be negative'

    return x ** 2

print(f(10))

Assertions can be skipped by running:
$ python -O raise.py