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Python Integration with Archer

Archer offers seamless integration with Python, enabling users to incorporate Python scripts into their Archer models directly. This guide provides a detailed explanation of this integration, showcasing its versatility and ease of use.

Including a Python Script

To bring a Python script into your Archer model, utilize the import directive:

model Phone {
import "" // Reference to the Python script

Phone - mandatory -> Screen

Sample Python Script

Consider the following Python script:

def method_after_update():
values = fetchValuesFromExternalApi()
sumOfValues = sum(values)

assign_property('Feature1.ExternalValues', values)

add_constraint(lambda: model.Feature2.Value > sumOfValues)

This script highlights the three primary features of Archer's Python integration:

  1. Event hooks: Call Python functions at specific points in the configuration's lifecycle.
  2. Direct Property Assignment: You can assign values from your Python script directly to variables in your Archer model, using the assign_property method.
  3. Constraint Addition: Use the add_constraint function to introduce new constraints.

Accessing and Setting Variable Properties

The Python integration introduces a global model object. Through this, you can interface with Archer model variables.

value = model['VariableName']['Value']

Note: The Selected and Value properties start with uppercase letters.

To assign a value to a model variable's property:

valueCalculatedFromApi = fetchValueFromApi()

assign_property('VariableName.PropertyName', valueCalculatedFromApi)

Python integration supports assignment of intricate object structures, including arrays:

assign_property('VariableName.ComplexObjectPropertyName', {
'NestedObject': {
ExampleValue: 123,
ExampleArray: [1, 2, 3],
'NestedNestedObject': {
ObjectValue: True

Such complex structures are fully accessible within your Archer model:

model Example {
Example - mandatory -> VariableName
Example - optional -> Option1

// Option1 visibility is contingent upon ObjectValue being true
condition Option1 = VariableName.NestedObject.NestedNestedObject.ObjectValue

// Using values from ExampleArray to determine Option1's lower bound value
forall v in VariableName.NestedObject.ExampleArray {
lower_bound Option1 = v * 2

Incorporating Additional Constraints

Augment your Archer model with constraints defined in Python:

pythonValue = 123

add_constraint(lambda: model['Variable1']['Value'] >= model['Variable2']['Value'] * pythonValue)

Using the traverse Method

The traverse method facilitates iteration over child variables of a given parent variable:

Given this Archer model:

model Example {
Example - mandatory -> Group
Group - optional -> Option1
Group - optional -> Option2
Group - optional -> Option3

You can loop over all of Group's options:

for c in traverse(model['Group']):
add_constraint(lambda: c.Value > 10)

Available hooks:

Before update@before_updateInvoked before a user requirement is updated in the solver.
After update@after_updateInvoked after a user requirement is updated in the solver.