A minor but useful recent addition to Python’s syntax, positional-only parameters, lets you indicate which function parameters must be specified as positional ones, never as keyword arguments.

Each key is associated with a value, which can be any Python object. You use a key to obtain its related values, and the lookup time for each key/value pair is highly constant.

I'll want to implement the retrieval as a function, and then invoke that function along with one argument—the URL I want to retrieve. I then can invoke that function by creating a new instance of ...