Question

I was wondering for a few ways to accomplish abstracting the data storage access away from the main application and a small example, an IoC framework seems overkill, maybe passing object via constructor parameter (facade).

is the below pseudo-code a good way to do things and how do i fill in the missing pieces with python?

main.py
    resp = Repository(engine=NoSql)  # can easily switch to nosql???
    resp.save("hello");
    resp.select("hello");

repository.py
class Repository:
    def __init__(self, engine):
        self.engine = engine

    def save(self, str)
        engine.save(str)

    def select(self, str)
        engine.select(str)

nosql.py
class NoSql:
    def save(self, str)
        nosql.save(str)

    def select(self, str)
        nosql.select(str)

mysql.py
class MySql:
    def save(self, str)
        mysql.save(str)

    def select(self, str)
        mysql.select(str)

Answer 1

I’d say the above isn’t a great way to go about it. The consumer (in this case main.py) shouldn’t know anything about the model’s implementation details. What I might do is store key/value pairs in an external configuration file to be used by the model to determine the engine to use.