ENH: Support objects with __array__ method (#625)

.isort.cfg

@@ -1,6 +1,6 @@
 [settings]
 line_length=88
 multi_line_output=3
-known_third_party=mock,numpy,pkg_resources,pytest,setuptools
+known_third_party=mock,numpy,pkg_resources,pytest,setuptools,xarray,pandas
 known_first_party=pyproj,test
 include_trailing_comma=true

docs/history.rst

@@ -5,6 +5,7 @@ Change Log
 -----
 * Minimum supported Python version 3.6 (issue #499)
 * Refactor Proj to inherit from Transformer (issue #624)
+* ENH: Support obects with '__array__' method (pandas.Series, xarray.DataArray, dask.array.Array) (issue #573)
 
 2.6.1
 ~~~~~

pyproj/utils.py

@@ -30,7 +30,11 @@ def _copytobuffer(xx: Any) -> Tuple[Any, bool, bool, bool]:
     isfloat = False
     islist = False
     istuple = False
-    # first, if it's a numpy array scalar convert to float
+    # check for pandas.Series, xarray.DataArray or dask.array.Array
+    if hasattr(xx, "__array__") and callable(xx.__array__):
+        xx = xx.__array__()
+
+    # if it's a numpy array scalar convert to float
     # (array scalars don't support buffer API)
     if hasattr(xx, "shape"):
         if xx.shape == ():
@@ -56,7 +60,10 @@ def _copytobuffer(xx: Any) -> Tuple[Any, bool, bool, bool]:
                     # inx,isfloat,islist,istuple
                     return inx, False, False, False
                 except Exception:
-                    raise TypeError("input must be an array, list, tuple or scalar")
+                    raise TypeError(
+                        "input must be an array, list, tuple, scalar, "
+                        "or have the __array__ method."
+                    )
     else:
         # perhaps they are regular python arrays?
         if hasattr(xx, "typecode"):

requirements-dev.txt

@@ -1,5 +1,5 @@
 cython>=0.28.4
-black; python_version >= '3.6'
+black
 flake8
 mock
 mypy
@@ -9,3 +9,4 @@ pytest>3.6
 pytest-cov
 shapely
 pre-commit
+xarray

test/test_utils.py

@@ -2,6 +2,8 @@
 
 import numpy
 import pytest
+from pandas import Series
+from xarray import DataArray
 
 from pyproj.utils import _copytobuffer, _copytobuffer_return_scalar
 
@@ -20,6 +22,7 @@ def test__copytobuffer_return_scalar__invalid():
     "in_data, is_float, is_list, is_tuple",
     [
         (numpy.array(1), True, False, False),
+        (DataArray(numpy.array(1)), True, False, False),
         (1, True, False, False),
         ([1], False, True, False),
         ((1,), False, False, True),
@@ -29,9 +32,16 @@ def test__copytobuffer(in_data, is_float, is_list, is_tuple):
     assert _copytobuffer(in_data) == (array("d", [1]), is_float, is_list, is_tuple)
 
 
-def test__copytobuffer__numpy_array():
-    in_arr = numpy.array([1])
-    assert _copytobuffer(in_arr) == (in_arr.astype("d"), False, False, False)
+@pytest.mark.parametrize(
+    "in_arr", [numpy.array([1]), DataArray(numpy.array([1])), Series(numpy.array([1]))],
+)
+def test__copytobuffer__numpy_array(in_arr):
+    assert _copytobuffer(in_arr) == (
+        in_arr.astype("d").__array__(),
+        False,
+        False,
+        False,
+    )
 
 
 def test__copytobuffer__invalid():