python/src/nanoarrow/lib.py

# 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 ._lib import Schema, Array, ArrayStream


def schema(obj):
    if isinstance(obj, Schema):
        return obj

    # Not particularly safe because _export_to_c() could be exporting an
    # array, schema, or array_stream. The ideal
    # solution here would be something like __arrow_c_schema__()
    if hasattr(obj, "_export_to_c"):
        out = Schema.allocate()
        obj._export_to_c(out._addr())
        return out
    else:
        raise TypeError(
            f"Can't convert object of type {type(obj).__name__} to nanoarrow.Schema"
        )


def array(obj):
    if isinstance(obj, Array):
        return obj

    # Somewhat safe because calling _export_to_c() with two arguments will
    # not fail with a crash (but will fail with a confusing error). The ideal
    # solution here would be something like __arrow_c_array__()
    if hasattr(obj, "_export_to_c"):
        out = Array.allocate(Schema.allocate())
        obj._export_to_c(out._addr(), out.schema._addr())
        return out
    else:
        raise TypeError(
            f"Can't convert object of type {type(obj).__name__} to nanoarrow.Array"
        )


def array_stream(obj):
    if isinstance(obj, Schema):
        return obj

    # Not particularly safe because _export_to_c() could be exporting an
    # array, schema, or array_stream. The ideal
    # solution here would be something like __arrow_c_array_stream__()
    if hasattr(obj, "_export_to_c"):
        out = ArrayStream.allocate()
        obj._export_to_c(out._addr())
        return out
    else:
        raise TypeError(
            f"Can't convert object of type {type(obj).__name__} to nanoarrow.ArrowArrayStream"
        )