Configuration is information that tells a program how to behave. A dictionary can hold choices and outcomes separately from the code that uses them, much like a menu separates available options from the process of taking an order. This makes behavior easier to read, change, and extend than a growing chain of conditional statements. section 7.1.2
A practical configuration pattern helps you:
- Map an input value directly to an outcome, such as a choice letter to a message. section 7.1.2
- Extract response formats into a dictionary and use a default when a request is unknown. section 9.2.1
- Add a new behavior by adding a mapping, rather than adding another conditional branch. section 7.1.2 section 9.2.2
Mapping choices to messages
Instead of writing several conditional branches, keep the choices in data:\n\nchoices = {'A': 'apples', 'B': 'bats'}\nprint(f'{choice} is for {choices[choice]}')\n\nThe program now has one stable execution step and a configuration mapping that can grow independently. section 7.1.2
Listing 9.3. An endpoint with extracted configuration
...
def random_food(request):
food = random.choice(FOODS)
formats = { #1
'application/json': json.dumps({'food': food}),
'application/xml': f'<response><food>{food}</food></response>',
}
return formats.get(request.headers.get('Accept'), food) #2
Compare an endpoint that stores JSON and XML response behavior in a dictionary, then selects the matching format or returns a default. section 9.2.1
