cheatsheet.txt

import math

try:
    print(math.sqrt(-9))
except ValueError:
    print("inf")
else:
    print("fine")
finally:
    print("the end")

A:
inf
the end

exception_handling.txt

# Incorrect number of arguments handling
# With sys.exit(1) we cause the script to
# exit

try:
    name = sys.argv[1]
except IndexError:
    print("Error: please provide a name and a repeat count to the script.")
    sys.exit(1)

# Handling 2 types of exceptions. IndexError is raised because incorrect
# number of args. ValueError is raised because of arg not being integer
try:
    repeat_count = int(sys.argv[2])
except IndexError:
    print("Error: please provide a name and a repeat count to the script.")
    sys.exit(1)
except ValueError:
    print("Error: the repeat count needs to be a number.")
    sys.exit(1)

# Handling errors when writing into a file.
# Because it can throw different exceptionsm when need the
# code being capable of dealing with the different types
# 'else' block will contain the code to be executed if not errors
# thrown
try:
    f = open("root_files/name_repeated.txt", "w")
except (OSError, IOError) as err:
    print("Error: unable to write file (", err, ")")
    for i in range(1, repeat_count + 1):
        print(i, "-", name)
else:
    names = [name + "\n" for i in range(1, repeat_count + 1)]
    f.writelines(names)
    f.close()

keyerror_exceptions.py

# This exception has to do when a certain key in a dict does not exist
# ages.py

ages = {'Jim': 30, 'Pam': 28, 'Kevin': 33}
person = input('Get age for: ')

try:
    print(f'{person} is {ages[person]} years old.')
except KeyError:
    print(f"{person}'s age is unknown.")

using_try.py

#using_try.py

import sys
import random

try:
    print(f"First argument {sys.argv[1]}")
    args = sys.argv
    random.shuffle(args)
    print(f"Random argument {args[0]}")
except (IndexError, KeyError) as err:
    print(f"Error: no arguments, please provide at least one argument ({err})")
except NameError:
    print(f"Error: random module not loaded")
else:
    print("Else is running")
finally:
    print("Finally is running")
"""
We did import random so that it is possible to successfully run the script. Let's give this a run to see how it goes:

$ python3.7 using_try.py
Error: no arguments, please provide at least one argument (list index out of range)
Finally is running
$ python3.7 using_try.py testing
First argument testing
Random argument using_try.py
Else is running
Finally is running
$
"""