Reforms improvement (#230)

* Add option for loading from dataframe

* Improve flexibility of reforms

* Versioning

changelog_entry.yaml

@@ -0,0 +1,4 @@
+- bump: minor
+  changes:
+    changed:
+    - Reform syntax to increase flexibility.

docs/python_api/reforms.ipynb

@@ -0,0 +1,124 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Reforms\n",
+    "\n",
+    "To define a reform, simply define a class inheriting from `Reform` with an `apply(self)` function. Inside it, `self` is the tax-benefit system attached to the simulation with loaded data `self.simulation: Simulation`. From this, you can run any kind of modification on the `Simulation` instance that you like- modify parameters, variable logic or even adjust simulation data."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from policyengine_core.country_template import Microsimulation\n",
+    "from policyengine_core.model_api import *\n",
+    "\n",
+    "baseline = Microsimulation()\n",
+    "\n",
+    "\n",
+    "class reform(Reform):\n",
+    "    def apply(self):\n",
+    "        simulation = self.simulation\n",
+    "\n",
+    "        # Modify parameters\n",
+    "\n",
+    "        simulation.tax_benefit_system.parameters.taxes.housing_tax.rate.update(\n",
+    "            20\n",
+    "        )\n",
+    "\n",
+    "        # Modify simulation data\n",
+    "\n",
+    "        salary = simulation.calculate(\"salary\", \"2022-01\")\n",
+    "\n",
+    "        new_salary = salary * 1.1\n",
+    "\n",
+    "        simulation.set_input(\"salary\", \"2022-01\", new_salary)\n",
+    "\n",
+    "\n",
+    "reformed = Microsimulation(reform=reform)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "(   value     weight\n",
+       " 0  110.0  1000000.0\n",
+       " 1    0.0  1000000.0\n",
+       " 2  220.0  1200000.0,\n",
+       "    value     weight\n",
+       " 0  100.0  1000000.0\n",
+       " 1    0.0  1000000.0\n",
+       " 2  200.0  1200000.0)"
+      ]
+     },
+     "execution_count": 2,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "reformed.calculate(\"salary\", \"2022-01\"), baseline.calculate(\n",
+    "    \"salary\", \"2022-01\"\n",
+    ")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "(    value     weight\n",
+       " 0  4000.0  1000000.0\n",
+       " 1  6000.0  1200000.0,\n",
+       "     value     weight\n",
+       " 0  2000.0  1000000.0\n",
+       " 1  3000.0  1200000.0)"
+      ]
+     },
+     "execution_count": 4,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "reformed.calculate(\"housing_tax\", 2022), baseline.calculate(\n",
+    "    \"housing_tax\", 2022\n",
+    ")"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "base",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.9.19"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}

policyengine_core/country_template/data/datasets/country_template_dataset.py

@@ -29,6 +29,7 @@ def generate(self) -> None:
             "person_household_id": {ETERNITY: person_household_id},
             "person_household_role": {ETERNITY: person_household_role},
             "salary": {salary_time_period: salary},
+            "accommodation_size": {salary_time_period: [200, 300]},
             "household_weight": {weight_time_period: weight},
         }
         self.save_dataset(data)

policyengine_core/data/dataset.py

@@ -363,3 +363,26 @@ def from_file(file_path: str, time_period: str = None):
         )()
 
         return dataset
+
+    @staticmethod
+    def from_dataframe(dataframe: pd.DataFrame, time_period: str = None):
+        """Creates a dataset from a DataFrame.
+
+        Returns:
+            Dataset: The dataset.
+        """
+        file_path = Path(file_path)
+        dataset = type(
+            "Dataset",
+            (Dataset,),
+            {
+                "name": file_path.stem,
+                "label": file_path.stem,
+                "data_format": Dataset.FLAT_FILE,
+                "file_path": "dataframe",
+                "time_period": time_period,
+                "load": lambda: dataframe,
+            },
+        )()
+
+        return dataset

policyengine_core/parameters/parameter.py

@@ -137,7 +137,7 @@ def clone(self):
         ]
         return clone
 
-    def update(self, period=None, start=None, stop=None, value=None):
+    def update(self, value=None, period=None, start=None, stop=None):
         """
         Change the value for a given period.
 
@@ -156,7 +156,7 @@ def update(self, period=None, start=None, stop=None, value=None):
             start = period.start
             stop = period.stop
         if start is None:
-            raise ValueError("You must provide either a start or a period")
+            start = "0000-01-01"
         start_str = str(start)
         stop_str = str(stop.offset(1, "day")) if stop else None
 

policyengine_core/reforms/reform.py

@@ -1,10 +1,13 @@
 from __future__ import annotations
 
 import copy
-from typing import Callable, Union
+from typing import Callable, Union, TYPE_CHECKING
 
 from policyengine_core.parameters import ParameterNode, Parameter
 from policyengine_core.taxbenefitsystems import TaxBenefitSystem
+
+if TYPE_CHECKING:
+    from policyengine_core.simulations import Simulation
 from policyengine_core.periods import (
     period as period_,
     instant as instant_,
@@ -60,6 +63,8 @@ class Reform(TaxBenefitSystem):
     parameter_values: dict = None
     """The parameter values of the reform. This is used to inform any calls to the PolicyEngine API."""
 
+    simulation: "Simulation" = None
+
     def __init__(self, baseline: TaxBenefitSystem):
         """
         :param baseline: Baseline TaxBenefitSystem.

policyengine_core/simulations/simulation.py

@@ -85,7 +85,6 @@ def __init__(
         reform: Reform = None,
         trace: bool = False,
     ):
-        reform_applied_after = False
         if tax_benefit_system is None:
             if (
                 self.default_tax_benefit_system_instance is not None
@@ -94,20 +93,11 @@ def __init__(
                 tax_benefit_system = self.default_tax_benefit_system_instance
             else:
                 # If reform is taken as an arg, pass it
-                try:
-                    tax_benefit_system = self.default_tax_benefit_system(
-                        reform=reform
-                    )
-                except:
-                    tax_benefit_system = self.default_tax_benefit_system()
-                    reform_applied_after = True
+                tax_benefit_system = self.default_tax_benefit_system()
             self.tax_benefit_system = tax_benefit_system
 
         self.reform = reform
         self.tax_benefit_system = tax_benefit_system
-
-        if reform_applied_after and reform is not None:
-            self.apply_reform(reform)
         self.branch_name = "default"
 
         if dataset is None:
@@ -169,6 +159,11 @@ def __init__(
                 self.dataset = dataset
             self.build_from_dataset()
 
+        self.tax_benefit_system.simulation = self
+
+        if self.reform is not None:
+            self.tax_benefit_system.apply_reform_set(self.reform)
+
         # Backwards compatibility methods
         self.calc = self.calculate
         self.df = self.calculate_dataframe