ARROW-18152: [Python] DataFrame Interchange Protocol for pyarrow Table

python/pyarrow/interchange/__init__.py

@@ -0,0 +1,16 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.

python/pyarrow/interchange/buffer.py

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+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+from __future__ import annotations
+import enum
+
+import pyarrow as pa
+
+
+class DlpackDeviceType(enum.IntEnum):
+    """Integer enum for device type codes matching DLPack."""
+
+    CPU = 1
+    CUDA = 2
+    CPU_PINNED = 3
+    OPENCL = 4
+    VULKAN = 7
+    METAL = 8
+    VPI = 9
+    ROCM = 10
+
+
+class _PyArrowBuffer:
+    """
+    Data in the buffer is guaranteed to be contiguous in memory.
+    Note that there is no dtype attribute present, a buffer can be thought of
+    as simply a block of memory. However, if the column that the buffer is
+    attached to has a dtype that's supported by DLPack and ``__dlpack__`` is
+    implemented, then that dtype information will be contained in the return
+    value from ``__dlpack__``.
+    This distinction is useful to support both data exchange via DLPack on a
+    buffer and (b) dtypes like variable-length strings which do not have a
+    fixed number of bytes per element.
+    """
+
+    def __init__(self, x: pa.Buffer, allow_copy: bool = True) -> None:
+        """
+        Handle PyArrow Buffers.
+        """
+        self._x = x
+
+    @property
+    def bufsize(self) -> int:
+        """
+        Buffer size in bytes.
+        """
+        return self._x.size
+
+    @property
+    def ptr(self) -> int:
+        """
+        Pointer to start of the buffer as an integer.
+        """
+        return self._x.address
+
+    def __dlpack__(self):
+        """
+        Produce DLPack capsule (see array API standard).
+        Raises:
+            - TypeError : if the buffer contains unsupported dtypes.
+            - NotImplementedError : if DLPack support is not implemented
+        Useful to have to connect to array libraries. Support optional because
+        it's not completely trivial to implement for a Python-only library.
+        """
+        raise NotImplementedError("__dlpack__")
+
+    def __dlpack_device__(self) -> tuple[DlpackDeviceType, int | None]:
+        """
+        Device type and device ID for where the data in the buffer resides.
+        Uses device type codes matching DLPack.
+        Note: must be implemented even if ``__dlpack__`` is not.
+        """
+        if self._x.is_cpu:
+            return (DlpackDeviceType.CPU, None)
+        else:
+            raise NotImplementedError("__dlpack_device__")
+
+    def __repr__(self) -> str:
+        return (
+            "PyArrowBuffer(" +
+            str(
+                {
+                    "bufsize": self.bufsize,
+                    "ptr": self.ptr,
+                    "device": self.__dlpack_device__()[0].name,
+                }
+            ) +
+            ")"
+        )