Scenario Copy Utility

Motivation

When running experiment sweeps, ablations, or parameter tuning, it is common to create multiple variants of a base scenario with small parameter changes.

Manually reconstructing scenarios is:

• Error-prone: Forgetting to update _scenario_id or other hidden attributes can cause subtle bugs.
• Verbose: Loops to create multiple scenario variants become messy and repetitive.

This utility introduces a simple, explicit API for cloning scenarios while preserving reproducibility guarantees.

Implementation

• Added a copy(**updates) method to the Scenario class.
• Behavior of copied scenario:
  • Receives a new _scenario_id
  • Does not retain the model reference
  • Shares the same RNG object by reference (explicitly documented)
  • Allows parameter overrides at creation

Examples

Without Copy

# This won't run
base = Scenario(a=1, b=2, rng=42)
scenarios2 = []
for b in [3, 4, 5]:
    params = base.to_dict() 
    scenarios2.append(Scenario(**params, b= b)) 

It has three problems

1. TypeError: experimental.scenarios.scenario.Scenario() got multiple values for keyword argument 'b'
2. _scenario_id of all scenerios would be same

# Solution
base = Scenario(a=1, b=2, rng=42)
scenarios2 = []
for b in [3, 4, 5]:
    params = base.to_dict()
    params.pop('_scenario_id', None) # fixes 2 
    params.update({'b': b})
    scenarios2.append(Scenario(**params)) 

3. Too Verbose

With Copy

base = Scenario(a=1, b=2, rng=42)
scenarios1 = [base.copy(b=b) for b in [3, 4, 5]]

Additional Context

• Dropped get_parameters as it is redundant on quaquel suggestion.
• I am not sure why are we copying _scenerio_id from *kwargs in scenerio class initialization

self._scenario_id: int = (
            next(self._ids[self.__class__])
            if "_scenario_id" not in kwargs
            else kwargs.pop("_scenario_id")
        )

solves #3159.