fix: pandas and double nested vectors issue 885 (#912)

* fix: pandas and double nested vectors issue 885

* style: pre-commit fixes

* Rename test file to match PR number.

* Fix ROOT import.

* Fix order of operations.

* Fix order of operations.2

* style: pre-commit fixes

* Change the logic in pandas finalize.

* style: pre-commit fixes

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

src/uproot/interpretation/library.py

@@ -841,14 +841,16 @@ def finalize(self, array, branch, interpretation, entry_start, entry_stop, optio
         ):
             return pandas.Series(array, index=index)
         else:
-            awkward_pandas = uproot.extras.awkward_pandas()
-            ak_lib = _libraries[Awkward.name]
-            ak_arr = ak_lib.finalize(
+            array = _libraries[Awkward.name].finalize(
                 array, branch, interpretation, entry_start, entry_stop, options
             )
-            return pandas.Series(
-                awkward_pandas.AwkwardExtensionArray(ak_arr), index=index
-            )
+            if isinstance(
+                array.type.content, uproot.extras.awkward().types.NumpyType
+            ) and array.layout.minmax_depth == (1, 1):
+                array = array.to_numpy()
+            else:
+                array = uproot.extras.awkward_pandas().AwkwardExtensionArray(array)
+        return pandas.Series(array, index=index)
 
     def group(self, arrays, expression_context, how):
         pandas = self.imported

src/uproot/interpretation/objects.py

@@ -135,7 +135,15 @@ def basket_array(
         )
         assert basket.byte_offsets is not None
 
-        if self._forth and isinstance(library, uproot.interpretation.library.Awkward):
+        if self._forth and (
+            isinstance(
+                library,
+                (
+                    uproot.interpretation.library.Awkward,
+                    uproot.interpretation.library.Pandas,
+                ),
+            )
+        ):
             output = self.basket_array_forth(
                 data,
                 byte_offsets,
@@ -403,9 +411,14 @@ def final_array(
             output = numpy.array([], dtype=self.numpy_dtype)
         elif all(
             uproot._util.from_module(x, "awkward") for x in basket_arrays.values()
+        ) and isinstance(
+            library,
+            (
+                uproot.interpretation.library.Awkward,
+                uproot.interpretation.library.Pandas,
+            ),
         ):
-            assert isinstance(library, uproot.interpretation.library.Awkward)
-            awkward = library.imported
+            awkward = uproot.extras.awkward()
             output = awkward.concatenate(trimmed, mergebool=False, highlevel=False)
         else:
             output = numpy.concatenate(trimmed)

tests/test_0910-fix_906_members_non_numerical_branches.py

@@ -1,5 +1,6 @@
-import uproot
+# BSD 3-Clause License; see https://github.com/scikit-hep/uproot5/blob/main/LICENSE
 
+import uproot
 from skhep_testdata import data_path
 
 

tests/test_0912-fix-pandas-and-double-nested-vectors-issue-885.py

@@ -0,0 +1,54 @@
+# BSD 3-Clause License; see https://github.com/scikit-hep/uproot5/blob/main/LICENSE
+
+import uproot
+import pytest
+import skhep_testdata, os
+import numpy as np
+import awkward as ak
+
+ROOT = pytest.importorskip("ROOT")
+
+
+def test_pandas_and_double_nested_vectors_issue_885(tmp_path):
+    filename = os.path.join(
+        tmp_path, "uproot_test_pandas_and_double_nested_vectors.root"
+    )
+    f = ROOT.TFile(filename, "recreate")
+    t = ROOT.TTree("mytree", "example tree")
+
+    vec1 = ROOT.std.vector("double")()
+    vec2 = ROOT.std.vector("double")()
+    vec_vec = ROOT.std.vector(ROOT.std.vector("double"))()
+
+    for i in range(3):
+        vec1.push_back(i)
+    for i in range(5):
+        vec2.push_back(i)
+
+    vec_vec.push_back(vec1)
+    vec_vec.push_back(vec2)
+
+    a = np.array([1, 2, 3, 4], dtype=np.uint32)
+    avec = ROOT.std.vector("unsigned int")(a)
+
+    b = np.array([[[0, 1, 3], [4, 5, 6], [7, 8, 9]]], dtype=np.uint32)
+    bvec = ROOT.std.vector("unsigned int")(b)
+
+    t.Branch("2Dvector", vec_vec)
+    t.Branch("1Dvector", avec)
+    t.Branch("othervector", bvec)
+
+    nentries = 25
+    for i in range(nentries):
+        t.Fill()
+
+    f.Write()
+
+    with uproot.open(filename)["mytree"] as fs:
+        u = fs.arrays(["2Dvector", "1Dvector", "othervector"], library="pd")
+        assert isinstance(u["2Dvector"][0], ak.highlevel.Array)
+        assert isinstance(u["1Dvector"][0], ak.highlevel.Array)
+        assert isinstance(u["othervector"][0], ak.highlevel.Array)
+        assert ak.to_list(u["2Dvector"][0]) == [[0, 1, 2], [0, 1, 2, 3, 4]]
+        assert ak.to_list(u["1Dvector"][0]) == [1, 2, 3, 4]
+        assert ak.to_list(u["othervector"][0]) == [0, 1, 3, 4, 5, 6, 7, 8, 9]