kerno.web.to_dict module

A setup so you can have many, powerful to_dict() implementations.

Our main objective is to remove any JSON concerns from model classes. These should NOT contain as_dict() implementations because the system may need multiple converters for the same model – for instance, with varying fields, verbosities, levels of detail, optional inclusion of related entities etc.

It is bad if AVerySpecificModel.as_dict() needs a different signature to accept a parameter that all the other as_dict() methods do not need.

Here is the solution:

By using Reg we now have a to_dict(obj, flavor='', **kw) function that dispatches on the type of obj and flavor. This allows you to register more than one implementation (with a “flavor” name) for each of your model classes.

In order to understand this, you need to know what Reg does: multiple dispatch.

Our to_dict() function also has a default implementation, so it can be used directly.

This way you can create a situation in which:

to_dict(Address, flavor="")  # calls one implementation, and
to_dict(Person, flavor="")  # calls another implementation, and
to_dict(Person, flavor="table")   # calls yet another implementation.

If the user code omits the flavor argument, the default one – whose value is an empty string – gets used.

And because our to_dict() accepts keyword arguments, you can create a very powerful version of it, that can take such arguments as a repository, a user object, the current date etc.

Please see a usage example in our tests.

kerno.web.to_dict.excluding(blacklist: Sequence, keys: Iterable) → Iterable

kerno.web.to_dict.keys_from(obj: Any) → Iterable

Return the names of the instance variables of obj.

kerno.web.to_dict.only_relevant(keys: Iterable[str]) → Iterable[str]

Ignore strings that start in dunder (“__”) or in “_sa_”.

These are usually keeping SQLAlchemy state.

kerno.web.to_dict.reuse_dict(obj: Any, keys: Iterable = (), for_json: bool = True, sort: bool = True, **kw) → collections.OrderedDict

Dump the instance variables of obj into an OrderedDict.

This function is reusable and free of Reg dispatch.

If the for_json flag is True, convert certain types.

If the sort flag is True, sort the OrderedDict.

kerno.web.to_dict.to_dict(obj, flavor='', **kw)

Overloadable version of our function reuse_dict.

You can register your own implementations depending on obj and flavor.