[BUG] Issue with empty list as default argument to "create_scenario" function

[AshishKuls]

Describe the bug

Using an empty list [] as default argument to a function is not correct and causes unwanted behavior.

project_cards_list argument in create_scenario function

def create_scenario(
    base_scenario: dict = {},
    card_directory: str = "",
    tags: [str] = None,
    project_cards_list=[],
    glob_search="",
    validate_project_cards=True,
) -> Scenario:

create a scenario from base scenario:

scenario_1 = Scenario.create_scenario(base_scenario=base_scenario)
scenario_1.add_project_card_from_file(
    os.path.join(STPAUL_DIR, "project_cards", "1_simple_roadway_attribute_change.yml"),
    validate=False
)
scenario_1.apply_all_projects()
scenario_1.applied_projects

['6th St E Road Diet'] is the applied project

Next, create another scenario from base (without any project card):

scenario_2 = Scenario.create_scenario(base_scenario=base_scenario)
scenario_2.get_project_names()

scenario_2 already contains project ['6th St E Road Diet']

This is because the default parameters are only instantiated once. A new list is created once when the function is defined, and the same list is used in each successive call of the create_scenario function.

After creating the scenario_1, Scenario.create_scenario has this as function definition

<function network_wrangler.scenario.Scenario.create_scenario(base_scenario: 'dict' = {}, card_directory: 'str' = '', tags: '[str]' = None, project_cards_list=[<network_wrangler.projectcard.ProjectCard object at 0x00000251D27306A0>], glob_search='', validate_project_cards=True) -> 'Scenario'>

Status

• Defined
• Planned
• Implemented
• Tested

Triggering line of code

https://github.com/wsp-sag/network_wrangler/blob/master/network_wrangler/scenario.py#L229

Thoughts on resolution

The solution and the standard way of doing it right is to pass default argument as None instead of [] to the function.

def create_scenario(
        base_scenario: dict = {},
        card_directory: str = "",
        tags: [str] = None,
        project_cards_list = None,
        glob_search = "",
        validate_project_cards = True,
    ) -> Scenario:

...

if project_cards_list is None:
    project_cards_list = []

if project_cards_list:
            WranglerLogger.debug(
                "Adding project cards from List.\n{}".format(
                    ",".join([p.project for p in project_cards_list])
                )
            )

scenario = Scenario(base_scenario, project_cards=project_cards_list)

[AshishKuls]

cc @e-lo @DavidOry @i-am-sijia

[AshishKuls]

done.

[e-lo]

Fixed to None in v1.