From f0e97ba3e2b52e61da24409ebdca265c287413b6 Mon Sep 17 00:00:00 2001
From: MarcoGorelli <33491632+MarcoGorelli@users.noreply.github.com>
Date: Thu, 7 Dec 2023 13:11:13 +0000
Subject: [PATCH 1/2] add cast

---
 spec/API_specification/dataframe_api/column_object.py    | 8 ++++++++
 spec/API_specification/dataframe_api/dataframe_object.py | 8 ++++++++
 2 files changed, 16 insertions(+)

diff --git a/spec/API_specification/dataframe_api/column_object.py b/spec/API_specification/dataframe_api/column_object.py
index b3e10738..8d44672d 100644
--- a/spec/API_specification/dataframe_api/column_object.py
+++ b/spec/API_specification/dataframe_api/column_object.py
@@ -1057,3 +1057,11 @@ def persist(self) -> Self:
             at most once per dataframe, and as late as possible in the pipeline.
         """
         ...
+
+    def cast(self, dtype: DType) -> Self:
+        """Cast specified columns to specified dtypes.
+
+        Cross-kind casting (e.g. integer to string) is not supported and may
+        vary across implementations.
+        """
+        ...
diff --git a/spec/API_specification/dataframe_api/dataframe_object.py b/spec/API_specification/dataframe_api/dataframe_object.py
index 4e423fd2..6e0fd178 100644
--- a/spec/API_specification/dataframe_api/dataframe_object.py
+++ b/spec/API_specification/dataframe_api/dataframe_object.py
@@ -925,3 +925,11 @@ def persist(self) -> Self:
                         features.append(column_name)
         """
         ...
+
+    def cast(self, dtypes: Mapping[str, DType]) -> Self:
+        """Convert specified columns to specified dtypes.
+
+        Cross-kind casting (e.g. integer to string) is not supported and may
+        vary across implementations.
+        """
+        ...

From ebaeb67d1454d9840a7af05d41bd84eabe624103 Mon Sep 17 00:00:00 2001
From: MarcoGorelli <33491632+MarcoGorelli@users.noreply.github.com>
Date: Fri, 8 Dec 2023 11:18:25 +0000
Subject: [PATCH 2/2] note what may vary across implementations

---
 spec/API_specification/dataframe_api/column_object.py    | 6 ++++--
 spec/API_specification/dataframe_api/dataframe_object.py | 6 ++++--
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/spec/API_specification/dataframe_api/column_object.py b/spec/API_specification/dataframe_api/column_object.py
index 8d44672d..199f91d8 100644
--- a/spec/API_specification/dataframe_api/column_object.py
+++ b/spec/API_specification/dataframe_api/column_object.py
@@ -1061,7 +1061,9 @@ def persist(self) -> Self:
     def cast(self, dtype: DType) -> Self:
         """Cast specified columns to specified dtypes.
 
-        Cross-kind casting (e.g. integer to string) is not supported and may
-        vary across implementations.
+        The following is not specified and may vary across implementations:
+
+        - Cross-kind casting (e.g. integer to string, or to float)
+        - Behaviour in the case of overflows
         """
         ...
diff --git a/spec/API_specification/dataframe_api/dataframe_object.py b/spec/API_specification/dataframe_api/dataframe_object.py
index 6e0fd178..6255402b 100644
--- a/spec/API_specification/dataframe_api/dataframe_object.py
+++ b/spec/API_specification/dataframe_api/dataframe_object.py
@@ -929,7 +929,9 @@ def persist(self) -> Self:
     def cast(self, dtypes: Mapping[str, DType]) -> Self:
         """Convert specified columns to specified dtypes.
 
-        Cross-kind casting (e.g. integer to string) is not supported and may
-        vary across implementations.
+        The following is not specified and may vary across implementations:
+
+        - Cross-kind casting (e.g. integer to string, or to float)
+        - Behaviour in the case of overflows
         """
         ...