Programming Patterns

This page contains standard 'patterns'

Error checking

<priming read - do something the loop depends on>
while <condition based on something from above>:
    display error message
    <same as the priming read again>
do next thing now that you know the 'something' is valid

Example:

SECRET = 6
guess = int(input("? "))
while guess != SECRET:
    print("Guess again!")
    guess = int(input("? "))
print("You got it!")

Exception-based error checking

Example:

valid_input = False
while not valid_input:
    try:
        age = int(input("Age: "))
        valid_input = True
    except ValueError:  # or just  except:
        print("Invalid (not an integer)")
print("Next year you will be", age + 1)

Finding

Filtering

"Innocent until proven guilty" Boolean validating