python/pyarrow/tests/pyarrow_cython_example.pyx

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#
#   http://www.apache.org/licenses/LICENSE-2.0
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# distutils: language=c++
# cython: language_level = 3

from pyarrow.lib cimport *


def get_array_length(obj):
    # An example function accessing both the pyarrow Cython API
    # and the Arrow C++ API
    cdef shared_ptr[CArray] arr = pyarrow_unwrap_array(obj)
    if arr.get() == NULL:
        raise TypeError("not an array")
    return arr.get().length()


def make_null_array(length):
    # An example function that returns a PyArrow object without PyArrow
    # being imported explicitly at the Python level.
    cdef shared_ptr[CArray] null_array
    null_array.reset(new CNullArray(length))
    return pyarrow_wrap_array(null_array)


def cast_scalar(scalar, to_type):
    cdef:
        shared_ptr[CScalar] c_scalar
        shared_ptr[CDataType] c_type
        CCastOptions cast_options
        CDatum c_datum
        CResult[CDatum] c_cast_result

    c_scalar = pyarrow_unwrap_scalar(scalar)
    if c_scalar.get() == NULL:
        raise TypeError("not a scalar")
    c_type = pyarrow_unwrap_data_type(to_type)
    if c_type.get() == NULL:
        raise TypeError("not a type")

    c_datum = CDatum(c_scalar)
    cast_options = CCastOptions()
    cast_options.to_type = c_type
    c_cast_result = Cast(c_datum, cast_options)
    c_datum = GetResultValue(c_cast_result)
    return pyarrow_wrap_scalar(c_datum.scalar())