From 9b7d6cfb6cdbc381af8a15057bf4529b2f58e07e Mon Sep 17 00:00:00 2001
From: Johannes Alnes <johalnes@me.com>
Date: Fri, 15 Dec 2023 20:23:39 +0100
Subject: [PATCH 1/4] Added dataframe interchange protocol

---
 chainladder/core/base.py                | 22 +++++++++++++++
 chainladder/core/tests/test_triangle.py | 36 +++++++++++++++++++++++++
 chainladder/core/triangle.py            |  6 +++--
 3 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/chainladder/core/base.py b/chainladder/core/base.py
index 4362069e..960fe864 100644
--- a/chainladder/core/base.py
+++ b/chainladder/core/base.py
@@ -2,6 +2,8 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at https://mozilla.org/MPL/2.0/.
 import pandas as pd
+from packaging import version
+
 import numpy as np
 from chainladder.utils.cupy import cp
 from chainladder.utils.sparse import sp
@@ -402,7 +404,27 @@ def __array_ufunc__(self, ufunc, method, *inputs, **kwargs):
             return obj
         else:
             raise NotImplementedError()
+        
+    def _interchange_dataframe(self, data):
+        """
+        Convert an object supporting the __dataframe__ protocol to a pandas DataFrame.
+        Requires pandas version > 1.5.2.
+
+        Parameters:
+        data: Dataframe object supporting the __dataframe__ protocol.
 
+        Returns:
+        pd.DataFrame: A pandas DataFrame.
+        """
+        # Check if pandas version is greater than 1.5.2
+        if version.parse(pd.__version__) >= version.parse("1.5.2"):
+            return pd.api.interchange.from_dataframe(data)
+        
+        else:
+            # Raise an error prompting the user to upgrade pandas
+            raise NotImplementedError("Your version of pandas does not support the DataFrame interchange API. "
+                                    "Please upgrade pandas to a version greater than 1.5.2 to use this feature.")
+            
     def __array_function__(self, func, types, args, kwargs):
         from chainladder.utils.utility_functions import concat
 
diff --git a/chainladder/core/tests/test_triangle.py b/chainladder/core/tests/test_triangle.py
index 624c09c3..c623ff0d 100644
--- a/chainladder/core/tests/test_triangle.py
+++ b/chainladder/core/tests/test_triangle.py
@@ -1,5 +1,6 @@
 import chainladder as cl
 import pandas as pd
+import polars as pl
 import numpy as np
 import copy
 import pytest
@@ -745,6 +746,9 @@ def test_halfyear_development():
         ["2012-01-01", "2013-12-31", "incurred", 200.0],
     ]
 
+    df_polars = pl.DataFrame(data)
+    df_polars.columns = ["origin", "val_date", "idx", "value"]
+
     assert (
         type(
             cl.Triangle(
@@ -757,3 +761,35 @@ def test_halfyear_development():
             )
         )
     ) == cl.Triangle
+
+    assert (
+        type(
+            cl.Triangle(
+                data=df_polars,
+                index="idx",
+                columns="value",
+                origin="origin",
+                development="val_date",
+                cumulative=True,
+            )
+        )
+    ) == cl.Triangle
+
+    assert (
+            cl.Triangle(
+                data=pd.DataFrame(data, columns=["origin", "val_date", "idx", "value"]),
+                index="idx",
+                columns="value",
+                origin="origin",
+                development="val_date",
+                cumulative=True,
+            ) ==
+            cl.Triangle(
+                data=df_polars,
+                index="idx",
+                columns="value",
+                origin="origin",
+                development="val_date",
+                cumulative=True,
+            )
+    )
\ No newline at end of file
diff --git a/chainladder/core/triangle.py b/chainladder/core/triangle.py
index 25213529..b9e8cc0b 100644
--- a/chainladder/core/triangle.py
+++ b/chainladder/core/triangle.py
@@ -123,7 +123,9 @@ def __init__(
     ):
         if data is None:
             return
-
+        elif not isinstance(data, pd.DataFrame) and hasattr(data, "__dataframe__"):
+            data = self._interchange_dataframe(data)
+        
         index, columns, origin, development = self._input_validation(
             data, index, columns, origin, development
         )
@@ -270,7 +272,7 @@ def __init__(
             self.ddims = obj.ddims
             self.values = obj.values
             self.valuation_date = pd.Timestamp(options.ULT_VAL)
-
+    
     @staticmethod
     def _split_ult(data, index, columns, origin, development):
         """Deal with triangles with ultimate values"""

From c1fc99fad5c88c7e79327ec2e4d35b56fbfc0d12 Mon Sep 17 00:00:00 2001
From: Johannes Alnes <johalnes@me.com>
Date: Fri, 15 Dec 2023 20:34:22 +0100
Subject: [PATCH 2/4] Wrong docstring format

---
 chainladder/core/base.py | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/chainladder/core/base.py b/chainladder/core/base.py
index 960fe864..9d8c3109 100644
--- a/chainladder/core/base.py
+++ b/chainladder/core/base.py
@@ -410,11 +410,14 @@ def _interchange_dataframe(self, data):
         Convert an object supporting the __dataframe__ protocol to a pandas DataFrame.
         Requires pandas version > 1.5.2.
 
-        Parameters:
-        data: Dataframe object supporting the __dataframe__ protocol.
-
-        Returns:
-        pd.DataFrame: A pandas DataFrame.
+        Parameters
+        ----------
+        data :
+            Dataframe object supporting the __dataframe__ protocol.
+        Returns
+        -------
+        out: pd.DataFrame
+            A pandas DataFrame.
         """
         # Check if pandas version is greater than 1.5.2
         if version.parse(pd.__version__) >= version.parse("1.5.2"):

From 8e395072145ee20350cd263fa0de38140923b82c Mon Sep 17 00:00:00 2001
From: Johannes Alnes <johalnes@me.com>
Date: Fri, 15 Dec 2023 20:45:27 +0100
Subject: [PATCH 3/4] Forgot to add Polars as dependecy. Used in tests

---
 environment-dev.yaml  | 1 +
 environment-docs.yaml | 1 +
 2 files changed, 2 insertions(+)

diff --git a/environment-dev.yaml b/environment-dev.yaml
index 271c542f..06b56591 100644
--- a/environment-dev.yaml
+++ b/environment-dev.yaml
@@ -14,6 +14,7 @@ dependencies:
   - ipykernel
 
   - pandas
+  - polars
   - scikit-learn
   - sparse
   - numba
diff --git a/environment-docs.yaml b/environment-docs.yaml
index 031fd654..58e4d26a 100644
--- a/environment-docs.yaml
+++ b/environment-docs.yaml
@@ -11,6 +11,7 @@ dependencies:
   - git
 
   - pandas
+  - polars
   - scikit-learn
   - sparse
   - numba

From 63cea7f374142551f5d29f13213b0e2b24972ee4 Mon Sep 17 00:00:00 2001
From: Johannes Alnes <johalnes@me.com>
Date: Fri, 15 Dec 2023 20:59:15 +0100
Subject: [PATCH 4/4] Added polars to CI environments

---
 ci/environment-latest.yaml | 1 +
 ci/environment-test.yaml   | 1 +
 2 files changed, 2 insertions(+)

diff --git a/ci/environment-latest.yaml b/ci/environment-latest.yaml
index 3cdd8095..748ac087 100644
--- a/ci/environment-latest.yaml
+++ b/ci/environment-latest.yaml
@@ -6,6 +6,7 @@ channels:
 
 dependencies:
   - conda-forge::pandas>=2.0
+  - polars
   - scikit-learn>=0.23
   - sparse>=0.9
   - numba
diff --git a/ci/environment-test.yaml b/ci/environment-test.yaml
index 24d3dd07..623492dc 100644
--- a/ci/environment-test.yaml
+++ b/ci/environment-test.yaml
@@ -7,6 +7,7 @@ channels:
 
 dependencies:
   - pandas>=0.23
+  - polars>=0.16.2
   - scikit-learn>=0.23
   - sparse>=0.9
   - numba