norman

Norman

Norman provides a framework for creating complex data structures using an database-like approach. The range of potential application is wide, for example in-memory databases, multi-keyed dictionaries or node graphs. These applications are illustrated in the following examples.

Database

This is a small database for a personal library::

db = Database()

@db.add
class Book(Table):
    name = Field(unique=True)
    author = Field(index=True)

    def validate(self):
        assert isinstance(self.name, str)
        assert isinstance(self.author, Author)

@db.add
class Author(Table):
    surname = Field(unique=True)
    initials = Field(unique=True, default='')
    nationality = Field()
    books = Join(Book.author)

Multi-keyed Dictionary

This table can be used as a dictionary with three keys::

class MultiDict(Table):
    key1 = Field(unique=True)
    key2 = Field(unique=True)
    key3 = Field(unique=True)
    value = Field()

Values can be added by::

MultiDict(key1=4, key2='abc', key3=0, value='efg')

And queried by::

for m in (MultiDict.key1 == 4 & Multidict.key2 == 'abc'):
    print(m.value)

Node Graph

This is a graph, where each node can have many parent nodes and many children nodes::

class Link(Table):
    """
    Directional connections between nodes.
    """
    parent = Field(unique=True)
    child = Field(unique=True)

    def validate(self):
        assert isinstance(self.parent, Node)
        assert isinstance(self.child, Node)


class Node(Table):
    """
    Nodes in the graph.
    """
    parents = Join(query=lambda n: (Link.child == n).field('parent'))
    children = Join(query=lambda n: (Link.parent == n).field('child'))

    def validate_delete(self):
        # Delete all connecting links if a node is deleted
        (Link.parent == self).delete()
        (Link.child == self).delete()