From 28c53a49bc3e9bba7499f0f583a7b240e735cddf Mon Sep 17 00:00:00 2001
From: Abhayindia <abhaychaudharydps@gmail.com>
Date: Wed, 9 Sep 2026 21:47:47 +0900
Subject: [PATCH] rename PTF_formula to ptf_formula with a deprecation alias

---
 chainladder/development/barnzehn.py       |  4 ++--
 chainladder/utils/tests/test_utilities.py | 12 ++++++++++++
 chainladder/utils/utility_functions.py    | 15 +++++++++++++--
 3 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/chainladder/development/barnzehn.py b/chainladder/development/barnzehn.py
index 1f893667..8ccd1326 100644
--- a/chainladder/development/barnzehn.py
+++ b/chainladder/development/barnzehn.py
@@ -9,7 +9,7 @@
 from chainladder.development.glm import TweedieGLM
 from sklearn.linear_model import LinearRegression
 from sklearn.pipeline import Pipeline
-from chainladder.utils.utility_functions import PatsyFormula, PTF_formula
+from chainladder.utils.utility_functions import PatsyFormula, ptf_formula
 
 
 class BarnettZehnwirth(TweedieGLM):
@@ -162,7 +162,7 @@ def fit(self, X, y=None, sample_weight=None):
         tri = X.cum_to_incr().log()
         response = X.columns[0] if not self.response else self.response
         if not self.formula:
-            self.formula = PTF_formula(
+            self.formula = ptf_formula(
                 self.alpha, self.gamma, self.iota, dgrain=min(tri.development)
             )
         self.model_ = DevelopmentML(
diff --git a/chainladder/utils/tests/test_utilities.py b/chainladder/utils/tests/test_utilities.py
index 9a39eccc..23b0a7ff 100644
--- a/chainladder/utils/tests/test_utilities.py
+++ b/chainladder/utils/tests/test_utilities.py
@@ -1297,3 +1297,15 @@ def test_triangleweight_drop_valuation_all(raa: Triangle) -> None:
                 "1990",
             ]
         ).fit(raa)
+
+
+def test_ptf_formula_deprecated_alias() -> None:
+    """
+    PTF_formula should warn and return the same string as ptf_formula.
+    """
+    from chainladder.utils.utility_functions import PTF_formula, ptf_formula
+
+    args = dict(alpha=[0, 2], gamma=[0, 1, 2], iota=[0, 1], dgrain=12)
+    with pytest.warns(FutureWarning, match="ptf_formula"):
+        old = PTF_formula(**args)
+    assert old == ptf_formula(**args)
diff --git a/chainladder/utils/utility_functions.py b/chainladder/utils/utility_functions.py
index cca1dce9..9db92bfd 100644
--- a/chainladder/utils/utility_functions.py
+++ b/chainladder/utils/utility_functions.py
@@ -7,11 +7,12 @@
 import dill
 import json
 import os
-import numpy as np
 import warnings
+import numpy as np
 import pandas as pd
 
 from chainladder import __dt64_unit__, __dt64_dtype__
+from chainladder._config.deprecation import _deprecated_rename
 from chainladder.utils.sparse import sp
 from chainladder.utils.data._manifest import SAMPLES
 from io import StringIO
@@ -1084,7 +1085,7 @@ def model_diagnostics(
     return concat(triangles, 0)
 
 
-def PTF_formula(  # noqa: N802
+def ptf_formula(
     alpha: list = None, gamma: list = None, iota: list = None, dgrain: int = 12
 ):
     """
@@ -1124,6 +1125,16 @@ def PTF_formula(  # noqa: N802
     return ""
 
 
+@_deprecated_rename("ptf_formula", version="0.11.0")
+def PTF_formula(  # noqa: N802
+    alpha: list = None, gamma: list = None, iota: list = None, dgrain: int = 12
+):
+    """
+    Deprecated alias for :func:`ptf_formula`.
+    """
+    return ptf_formula(alpha=alpha, gamma=gamma, iota=iota, dgrain=dgrain)
+
+
 def date_delta_adjustment(date: str) -> str:
     """
     Subtracts the default pandas datetime delta from a date in "YYYY-MM-DD" string format.