Modify nodes and models

Traditionally, to modify a component of a pre-defined model, one has to rewrite the code. The approach is error-prone and not scalable. mmodel uses DAG to create modular models that allow easy modification of nodes and models post-definition using modifiers. A modifier is a decorator that can modify the function of a node or the model itself. For example, to add a loop modifier to the node “add”:

from mmodel import Graph, Node
G = Graph()


def add(a, b):
    """The sum of a and b."""
    return a + b


def squared(c):
    """The squared value of c."""
    return c**2


from mmodel.modifier import loop_input

G.add_edge("add", "squared")
# set object without modifiers
G.set_node_object(Node("squared", squared, "d"))

# set object with modifier
G.set_node_object(Node("add", add, "c", modifiers=[loop_input(parameter='b')]))

# post modification
# a new copy of the graph is created

H = G.edit_node("add", modifiers=[loop_input('b')])

Similarly, use the modifiers argument to define model modifiers.

Modifier chaining

Because the modifiers are decorators, they can be chained. The modifiers in the list are applied in the order of the modifiers argument.

See modifier API for modifier API, and modifier reference </ref_modifier> for all available modifiers.