Tax-benefit systems#

The policyengine_core.taxbenefitsystems module contains the definition of TaxBenefitSystem, the class that represents a country’s tax-benefit system: the logic, parameters and entities, not the input data.

TaxBenefitSystem#

class policyengine_core.taxbenefitsystems.tax_benefit_system.TaxBenefitSystem(entities: Optional[Sequence[policyengine_core.entities.entity.Entity]] = None, reform=None)[source]#

Bases: object

Represents the legislation.

It stores parameters (values defined for everyone) and variables (values defined for some given entity e.g. a person).

parameters#: Directory containing the YAML parameter files.

Parameters: entities – Entities used by the tax benefit system.

add_modelled_policy_metadata()[source]#: Adds metadata to variables that are modelled by PolicyEngine.

add_variable(variable: policyengine_core.variables.variable.Variable) → policyengine_core.variables.variable.Variable[source]#

Adds an OpenFisca variable to the tax and benefit system.

Parameters: variable – The variable to add. Must be a subclass of Variable.
Raises: policyengine_core.errors.VariableNameConflictError – if a variable with the same name have previously been added to the tax and benefit system.

add_variable_metadata_from_folder(file_path: str) → None[source]#: Adds metadata from a given README.md file to the tax and benefit system.

add_variables(*variables: List[Type[policyengine_core.variables.variable.Variable]])[source]#

Adds a list of OpenFisca Variables to the TaxBenefitSystem.

See also add_variable

add_variables_from_directory(directory: str) → None[source]#: Recursively explores a directory, and adds all OpenFisca variables found there to the tax and benefit system.

add_variables_from_file(file_path: str) → None[source]#: Adds all OpenFisca variables contained in a given file to the tax and benefit system.

apply_reform(reform_path: str) → policyengine_core.taxbenefitsystems.tax_benefit_system.TaxBenefitSystem[source]#

Generates a new tax and benefit system applying a reform to the tax and benefit system.

The current tax and benefit system is not mutated.

Parameters: reform_path – The reform to apply. Must respect the format installed_package.sub_module.reform
Returns: A reformed tax and benefit system.
Return type: TaxBenefitSystem

Example

>>> self.apply_reform('openfisca_france.reforms.inversion_revenus')

auto_carry_over_input_variables: bool = False#: Whether to automatically carry over input variables when calculating a variable for a period different from the period of the input variables.

basic_inputs: List[str] = None#: Short list of basic inputs to get medium accuracy.

entities: List[policyengine_core.entities.entity.Entity] = None#: The entities of the tax and benefit system.

get_package_metadata() → dict[source]#

Gets metatada relative to the country package the tax and benefit system is built from.

Returns: Country package metadata
Return type: dict

Example:

>>> tax_benefit_system.get_package_metadata()
>>> {
>>>    'location': '/path/to/dir/containing/package',
>>>    'name': 'openfisca-france',
>>>    'repository_url': 'https://github.com/openfisca/openfisca-france',
>>>    'version': '17.2.0'
>>>    }

get_parameters_at_instant(instant: policyengine_core.periods.instant_.Instant) → policyengine_core.parameters.parameter_node_at_instant.ParameterNodeAtInstant[source]#

Get the parameters of the legislation at a given instant

Parameters: instant – str of the format ‘YYYY-MM-DD’ or Instant instance.
Returns: The parameters of the legislation at a given instant.
Return type: ParameterNodeAtInstant

get_variable(variable_name: str, check_existence: bool = False) → policyengine_core.variables.variable.Variable[source]#

Get a variable from the tax and benefit system.

Parameters

variable_name – Name of the requested variable.
check_existence – If True, raise an error if the requested variable does not exist.

get_variables(entity: Optional[policyengine_core.entities.entity.Entity] = None) → dict[source]#

Gets all variables contained in a tax and benefit system.

Parameters: entity (Entity) – If set, returns only the variable defined for the given entity.
Returns: A dictionary, indexed by variable names.
Return type: dict

load_extension(extension: str) → None[source]#

Loads an extension to the tax and benefit system.

Parameters: extension (str) – The extension to load. Can be an absolute path pointing to an extension directory, or the name of an OpenFisca extension installed as a pip package.

load_parameters(path_to_yaml_dir: str) → None[source]#

Loads the legislation parameter for a directory containing YAML parameters files.

Parameters: path_to_yaml_dir – Absolute path towards the YAML parameter directory.

Example:

>>> self.load_parameters('/path/to/yaml/parameters/dir')

modelled_policies: str = None#: A YAML filepath containing metadata describing the modelled policies.

modify_parameters(modifier_function: Callable[[policyengine_core.parameters.parameter_node.ParameterNode], policyengine_core.parameters.parameter_node.ParameterNode]) → None[source]#

Make modifications on the parameters of the legislation.

Call this function in apply() if the reform asks for legislation parameter modifications.

Parameters: modifier_function – A function that takes a ParameterNode and should return an object of the same type.

neutralize_variable(variable_name: str) → None[source]#

Neutralizes an OpenFisca variable existing in the tax and benefit system.

A neutralized variable always returns its default value when computed.

Trying to set inputs for a neutralized variable has no effect except raising a warning.

parameters_dir: str = None#: Directory containing the YAML parameter tree.

replace_variable(variable: str) → policyengine_core.variables.variable.Variable[source]#

Replaces an existing OpenFisca variable in the tax and benefit system by a new one.

The new variable must have the same name than the replaced one.

If no variable with the given name exists in the tax and benefit system, no error will be raised and the new variable will be simply added.

Parameters: variable (Variable) – New variable to add. Must be a subclass of Variable.

update_variable(variable: str) → policyengine_core.variables.variable.Variable[source]#

Updates an existing OpenFisca variable in the tax and benefit system.

All attributes of the updated variable that are not explicitely overridden by the new variable will stay unchanged.

The new variable must have the same name than the updated one.

If no variable with the given name exists in the tax and benefit system, no error will be raised and the new variable will be simply added.

Parameters: variable (Variable) – Variable to add. Must be a subclass of Variable.

variables_dir: str = None#: Directory containing the Python files defining the variables of the tax and benefit system.