Add select_filing_status_value utility function

changelog_entry.yaml

@@ -0,0 +1,6 @@
+- bump: minor
+  changes:
+    added:
+      - Added select_filing_status_value utility function for cleaner filing status selection with SINGLE as default.
+    changed:
+      - Refactored MD, CA, NY, AL, GA income tax calculations to use select_filing_status_value utility.

policyengine_us/tests/tools/test_filing_status_utility.yaml

@@ -0,0 +1,55 @@
+# Test that select_filing_status_value works correctly with MD income tax
+- name: Test filing status utility with MD tax - single filer
+  period: 2024
+  input:
+    people:
+      person:
+        age: 30
+    tax_units:
+      tax_unit:
+        members: [person]
+        md_taxable_income: 50_000
+    households:
+      household:
+        members: [person]
+        state_code: MD
+  output:
+    md_income_tax_before_credits: 2_322.50
+
+- name: Test filing status utility with MD tax - joint filers
+  period: 2024
+  input:
+    people:
+      head:
+        age: 30
+      spouse:
+        age: 28
+    tax_units:
+      tax_unit:
+        members: [head, spouse]
+        md_taxable_income: 100_000
+    households:
+      household:
+        members: [head, spouse]
+        state_code: MD
+  output:
+    md_income_tax_before_credits: 4_697.50
+
+- name: Test filing status utility with MD tax - head of household
+  period: 2024
+  input:
+    people:
+      head:
+        age: 35
+      child:
+        age: 10
+    tax_units:
+      tax_unit:
+        members: [head, child]
+        md_taxable_income: 75_000
+    households:
+      household:
+        members: [head, child]
+        state_code: MD
+  output:
+    md_income_tax_before_credits: 3_510.00

policyengine_us/tools/general.py

@@ -84,3 +84,81 @@ def get_previous_threshold(
     return t[
         max_((t <= values.reshape((1, len(values))).T).sum(axis=1) - 1, 0)
     ]
+
+
+def select_filing_status_value(
+    filing_status: ArrayLike,
+    filing_status_values: dict,
+    input_value: ArrayLike = None,
+    **kwargs,
+) -> ArrayLike:
+    """
+    Select a value based on filing status, with SINGLE as the default.
+
+    This is a common pattern for selecting parameter values based on filing status.
+    According to IRS SOI data, SINGLE is the most common filing status.
+
+    Args:
+        filing_status: Array of filing status enum values
+        filing_status_values: Dict mapping filing status to values or functions
+        input_value: Optional input value to pass to functions (e.g., taxable income)
+
+    Returns:
+        Array of selected values based on filing status
+
+    Example:
+        # For parameter values
+        result = select_filing_status_value(
+            filing_status,
+            parameters.amount
+        )
+
+        # For calculated values (e.g., tax brackets)
+        result = select_filing_status_value(
+            filing_status,
+            parameters.rates,
+            taxable_income
+        )
+    """
+    statuses = filing_status.possible_values
+
+    # Helper function to get value
+    def get_value(fs_value):
+        if input_value is not None and hasattr(fs_value, "calc"):
+            # It's a rate schedule or similar
+            return fs_value.calc(input_value, **kwargs)
+        elif hasattr(fs_value, "__call__"):
+            # It's a callable
+            return (
+                fs_value(input_value, **kwargs)
+                if input_value is not None
+                else fs_value(**kwargs)
+            )
+        else:
+            # It's a simple value
+            return fs_value
+
+    # Build conditions and values, excluding SINGLE
+    conditions = []
+    values = []
+
+    # Check each filing status except SINGLE
+    for status_name in [
+        "JOINT",
+        "SEPARATE",
+        "HEAD_OF_HOUSEHOLD",
+        "SURVIVING_SPOUSE",
+    ]:
+        # Check if this enum value exists in this filing status enum
+        if hasattr(statuses, status_name):
+            status_enum = getattr(statuses, status_name)
+            if status_enum.name.lower() in filing_status_values:
+                conditions.append(filing_status == status_enum)
+                values.append(
+                    get_value(filing_status_values[status_enum.name.lower()])
+                )
+
+    # SINGLE is the default
+    default_value = get_value(filing_status_values["single"])
+
+    return select(conditions, values, default=default_value)

policyengine_us/variables/gov/states/al/tax/income/al_income_tax_before_non_refundable_credits.py

@@ -1,4 +1,5 @@
 from policyengine_us.model_api import *
+from policyengine_us.tools.general import select_filing_status_value
 
 
 class al_income_tax_before_non_refundable_credits(Variable):
@@ -16,21 +17,4 @@ def formula(tax_unit, period, parameters):
         taxable_income = tax_unit("al_taxable_income", period)
         p = parameters(period).gov.states.al.tax.income.rates
 
-        statuses = filing_status.possible_values
-
-        return select(
-            [
-                filing_status == statuses.SINGLE,
-                filing_status == statuses.SEPARATE,
-                filing_status == statuses.JOINT,
-                filing_status == statuses.SURVIVING_SPOUSE,
-                filing_status == statuses.HEAD_OF_HOUSEHOLD,
-            ],
-            [
-                p.single.calc(taxable_income),
-                p.separate.calc(taxable_income),
-                p.joint.calc(taxable_income),
-                p.surviving_spouse.calc(taxable_income),
-                p.head_of_household.calc(taxable_income),
-            ],
-        )
+        return select_filing_status_value(filing_status, p, taxable_income)

policyengine_us/variables/gov/states/ca/tax/income/ca_income_tax_before_credits.py

@@ -1,4 +1,5 @@
 from policyengine_us.model_api import *
+from policyengine_us.tools.general import select_filing_status_value
 
 
 class ca_income_tax_before_credits(Variable):
@@ -15,21 +16,4 @@ def formula(tax_unit, period, parameters):
         taxable_income = tax_unit("ca_taxable_income", period)
         p = parameters(period).gov.states.ca.tax.income.rates
 
-        statuses = filing_status.possible_values
-
-        return select(
-            [
-                filing_status == statuses.SINGLE,
-                filing_status == statuses.SEPARATE,
-                filing_status == statuses.JOINT,
-                filing_status == statuses.SURVIVING_SPOUSE,
-                filing_status == statuses.HEAD_OF_HOUSEHOLD,
-            ],
-            [
-                p.single.calc(taxable_income),
-                p.separate.calc(taxable_income),
-                p.joint.calc(taxable_income),
-                p.surviving_spouse.calc(taxable_income),
-                p.head_of_household.calc(taxable_income),
-            ],
-        )
+        return select_filing_status_value(filing_status, p, taxable_income)

policyengine_us/variables/gov/states/ga/tax/income/ga_income_tax_before_non_refundable_credits.py

@@ -1,4 +1,5 @@
 from policyengine_us.model_api import *
+from policyengine_us.tools.general import select_filing_status_value
 
 
 class ga_income_tax_before_non_refundable_credits(Variable):
@@ -12,21 +13,5 @@ class ga_income_tax_before_non_refundable_credits(Variable):
     def formula(tax_unit, period, parameters):
         p = parameters(period).gov.states.ga.tax.income.main
         filing_status = tax_unit("filing_status", period)
-        status = filing_status.possible_values
         income = tax_unit("ga_taxable_income", period)
-        return select(
-            [
-                filing_status == status.SINGLE,
-                filing_status == status.SEPARATE,
-                filing_status == status.JOINT,
-                filing_status == status.HEAD_OF_HOUSEHOLD,
-                filing_status == status.SURVIVING_SPOUSE,
-            ],
-            [
-                p.single.calc(income),
-                p.separate.calc(income),
-                p.joint.calc(income),
-                p.head_of_household.calc(income),
-                p.surviving_spouse.calc(income),
-            ],
-        )
+        return select_filing_status_value(filing_status, p, income)

policyengine_us/variables/gov/states/md/tax/income/md_income_tax_before_credits.py

@@ -1,4 +1,5 @@
 from policyengine_us.model_api import *
+from policyengine_us.tools.general import select_filing_status_value
 
 
 class md_income_tax_before_credits(Variable):
@@ -11,26 +12,12 @@ class md_income_tax_before_credits(Variable):
 
     def formula(tax_unit, period, parameters):
         filing_status = tax_unit("filing_status", period)
-        filing_statuses = filing_status.possible_values
         taxable_income = tax_unit("md_taxable_income", period)
 
         # Calculate regular income tax based on filing status
         p = parameters(period).gov.states.md.tax.income
-        regular_income_tax = select(
-            [
-                filing_status == filing_statuses.SINGLE,
-                filing_status == filing_statuses.SEPARATE,
-                filing_status == filing_statuses.JOINT,
-                filing_status == filing_statuses.HEAD_OF_HOUSEHOLD,
-                filing_status == filing_statuses.SURVIVING_SPOUSE,
-            ],
-            [
-                p.rates.single.calc(taxable_income),
-                p.rates.separate.calc(taxable_income),
-                p.rates.joint.calc(taxable_income),
-                p.rates.head_of_household.calc(taxable_income),
-                p.rates.surviving_spouse.calc(taxable_income),
-            ],
+        regular_income_tax = select_filing_status_value(
+            filing_status, p.rates, taxable_income
         )
 
         # Add capital gains surtax if applicable

policyengine_us/variables/gov/states/ny/tax/income/ny_main_income_tax.py

@@ -1,4 +1,5 @@
 from policyengine_us.model_api import *
+from policyengine_us.tools.general import select_filing_status_value
 
 
 class ny_main_income_tax(Variable):
@@ -12,28 +13,6 @@ class ny_main_income_tax(Variable):
     def formula(tax_unit, period, parameters):
         taxable_income = tax_unit("ny_taxable_income", period)
         filing_status = tax_unit("filing_status", period)
-        status = filing_status.possible_values
-
         rates = parameters(period).gov.states.ny.tax.income.main
-        single = rates.single
-        joint = rates.joint
-        hoh = rates.head_of_household
-        surviving_spouse = rates.surviving_spouse
-        separate = rates.separate
 
-        return select(
-            [
-                filing_status == status.SINGLE,
-                filing_status == status.JOINT,
-                filing_status == status.HEAD_OF_HOUSEHOLD,
-                filing_status == status.SURVIVING_SPOUSE,
-                filing_status == status.SEPARATE,
-            ],
-            [
-                single.calc(taxable_income),
-                joint.calc(taxable_income),
-                hoh.calc(taxable_income),
-                surviving_spouse.calc(taxable_income),
-                separate.calc(taxable_income),
-            ],
-        )
+        return select_filing_status_value(filing_status, rates, taxable_income)