Merge #187

187: Bugfix/fix 165 fill value must be scalar r=andrewgsavage a=burnpanck

- [x] Closes #165
- [x] Executed `pre-commit run --all-files` with no errors
- [x] The change is fully covered by automated unit tests
- [ ] ~Documented in docs/ as appropriate~
- [x] Added an entry to the CHANGES file

Co-authored-by: Yves Delley <delleyves@gmx.ch>

CHANGES

@@ -8,6 +8,7 @@ pint-pandas Changelog
 - Support for magnitudes of any type, such as complex128 or tuples #146
 - Support for Pint 0.21 #168, #179
 - Cast to `numpy.ndarray` in `PintArray._reduce` if needed to use `nanops` functions
+- Support for unit registries with `force_ndarray_like = True`. #165
 
 0.3 (2022-11-14)
 ----------------

pint_pandas/pint_array.py

@@ -458,13 +458,17 @@ def take(self, indices, allow_fill=False, fill_value=None):
         Examples
         --------
         """
-        from pandas.core.algorithms import take
+        from pandas.core.algorithms import take, is_scalar
 
         data = self._data
         if allow_fill and fill_value is None:
             fill_value = self.dtype.na_value
         if isinstance(fill_value, _Quantity):
             fill_value = fill_value.to(self.units).magnitude
+            if not is_scalar(fill_value) and not fill_value.ndim:
+                # deal with Issue #165; for unit registries with force_ndarray_like = True,
+                # magnitude is in fact an array scalar, which will get rejected by pandas.
+                fill_value = fill_value[()]
 
         result = take(data, indices, fill_value=fill_value, allow_fill=allow_fill)
 

pint_pandas/testsuite/test_issues.py

@@ -4,6 +4,7 @@
 import numpy as np
 import pandas as pd
 import pytest
+import pint
 from pandas.tests.extension.base.base import BaseExtensionTests
 from pint.testsuite import helpers
 
@@ -12,6 +13,43 @@
 ureg = PintType.ureg
 
 
+class TestIssue165(BaseExtensionTests):
+    def test_force_ndarray_like(self):
+        # store previous registries to undo our changes
+        prev_PintType_ureg = PintType.ureg
+        prev_appreg = pint.get_application_registry().get()
+        prev_cache = PintType._cache
+        try:
+            # create a temporary registry with force_ndarray_like = True (`pint_xarray` insists on that)
+            test_ureg = pint.UnitRegistry()
+            test_ureg.force_ndarray_like = True
+            # register
+            pint.set_application_registry(test_ureg)
+            PintType.ureg = test_ureg
+            # clear units cache
+            PintType._cache = {}
+
+            # run TestIssue21.test_offset_concat with our test-registry (one of many that currently fails with force_ndarray_like=True)
+            q_a = ureg.Quantity(np.arange(5), test_ureg.Unit("degC"))
+            q_b = ureg.Quantity(np.arange(6), test_ureg.Unit("degC"))
+            q_a_ = np.append(q_a, np.nan)
+
+            a = pd.Series(PintArray(q_a))
+            b = pd.Series(PintArray(q_b))
+
+            result = pd.concat([a, b], axis=1)
+            expected = pd.DataFrame(
+                {0: PintArray(q_a_), 1: PintArray(q_b)}, dtype="pint[degC]"
+            )
+            self.assert_equal(result, expected)
+
+        finally:
+            # restore registry
+            PintType.ureg = prev_PintType_ureg
+            PintType._cache = prev_cache
+            pint.set_application_registry(prev_appreg)
+
+
 class TestIssue21(BaseExtensionTests):
     @pytest.mark.filterwarnings("ignore::RuntimeWarning")
     def test_offset_concat(self):