DatabaseDict

class lsst.daf.butler.DatabaseDict(config, types, key, value)

Bases: collections.abc.MutableMapping

An abstract base class for dict-like objects with a specific key type and namedtuple values, backed by a database.

DatabaseDict subclasses must implement the abstract __getitem__, __setitem__, __delitem__`, ``__iter__, and __len__ abstract methods defined by MutableMapping.

They must also provide a constructor that takes the same arguments as that of DatabaseDict itself, unless they are constructed solely by Registry.makeDatabaseDict (in which case any constructor arguments are permitted).

Parameters:

config : Config

Configuration used to identify and construct a subclass.

types : dict

A dictionary mapping str field names to type objects, containing all fields to be held in the database.

key : str

The name of the field to be used as the dictionary key. Must not be present in value._fields.

value : type

The type used for the dictionary’s values, typically a namedtuple. Must have a _fields class attribute that is a tuple of field names (i.e. as defined by namedtuple); these field names must also appear in the types arg, and a _make attribute to construct it from a sequence of values (again, as defined by namedtuple).