Error on DataFrame#loc[] with an array

[mrkn]

>> df = Pandas::DataFrame.new([[*1..4], [*5..8], [*9..12]], index: %w[r1 r2 r3], columns: %w[x1 x2 x3 x4])
>> df[df % 3 == 1] = -1
>> df
=>
    x1  x2  x3  x4
r1  -1   2   3  -1
r2   5   6  -1   8
r3   9  -1  11  12
>> df.loc[["r3", "r1"]]
Traceback (most recent call last):
        6: from /Users/mrkn/.rbenv/versions/2.7/bin/irb:23:in `<main>'
        5: from /Users/mrkn/.rbenv/versions/2.7/bin/irb:23:in `load'
        4: from /Users/mrkn/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/irb-1.2.3/exe/irb:11:in `<top (required)>'
        3: from (irb):141
        2: from /Users/mrkn/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/pycall-1.3.0/lib/pycall/pyobject_wrapper.rb:79:in `[]'
        1: from /Users/mrkn/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/pycall-1.3.0/lib/pycall/pyobject_wrapper.rb:79:in `getitem'
/Users/mrkn/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/pycall-1.3.0/lib/pycall/list.rb:18: warning: Capturing the given block using Kernel#proc is deprecated; use `&block` instead
PyCall::PyError (<class 'KeyError'>: 'r1')
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexing.py", line 1762, in __getitem__
    return self._getitem_tuple(key)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexing.py", line 1272, in _getitem_tuple
    return self._getitem_lowerdim(tup)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexing.py", line 1421, in _getitem_lowerdim
    return getattr(section, self.name)[new_key]
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexing.py", line 1768, in __getitem__
    return self._getitem_axis(maybe_callable, axis=axis)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexing.py", line 1965, in _getitem_axis
    return self._get_label(key, axis=axis)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexing.py", line 621, in _get_label
    return self.obj._xs(label, axis=axis)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/generic.py", line 3537, in xs
    loc = self.index.get_loc(key)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexes/base.py", line 2648, in get_loc
    return self._engine.get_loc(self._maybe_cast_indexer(key))
  File "pandas/_libs/index.pyx", line 111, in pandas._libs.index.IndexEngine.get_loc
  File "pandas/_libs/index.pyx", line 138, in pandas._libs.index.IndexEngine.get_loc
  File "pandas/_libs/hashtable_class_helper.pxi", line 1619, in pandas._libs.hashtable.PyObjectHashTable.get_item
  File "pandas/_libs/hashtable_class_helper.pxi", line 1627, in pandas._libs.hashtable.PyObjectHashTable.get_item

The expected result is:

>> df.loc[["r3", "r1"]]
=>
    x1  x2  x3  x4
r3   9  -1  11  12
r1  -1   2   3  -1

[mrkn]

There is the same issue on iloc

>> df.iloc[[2, 0, 1]]
Traceback (most recent call last):
        7: from /Users/mrkn/.rbenv/versions/2.7/bin/irb:23:in `<main>'
        6: from /Users/mrkn/.rbenv/versions/2.7/bin/irb:23:in `load'
        5: from /Users/mrkn/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/irb-1.2.3/exe/irb:11:in `<top (required)>'
        4: from (irb):141
        3: from (irb):142:in `rescue in irb_binding'
        2: from /Users/mrkn/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/pycall-1.3.0/lib/pycall/pyobject_wrapper.rb:79:in `[]'
        1: from /Users/mrkn/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/pycall-1.3.0/lib/pycall/pyobject_wrapper.rb:79:in `getitem'
/Users/mrkn/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/pycall-1.3.0/lib/pycall/list.rb:18: warning: Capturing the given block using Kernel#proc is deprecated; use `&block` instead
PyCall::PyError (<class 'pandas.core.indexing.IndexingError'>: Too many indexers)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexing.py", line 1762, in __getitem__
    return self._getitem_tuple(key)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexing.py", line 2067, in _getitem_tuple
    self._has_valid_tuple(tup)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexing.py", line 701, in _has_valid_tuple
    raise IndexingError("Too many indexers")

The expected result is:

>> df.iloc[[2, 0, 1]]
=>
    x1  x2  x3  x4
r3   9  -1  11  12
r1  -1   2   3  -1
r2   5   6  -1   8

[mrkn]

Other examples.

I expect the following results.

>> df.loc["r2", ["x3", "x1"]]
=>
x3   -1
x1    5
Name: r2, dtype: int64

>> df.iloc[[2, 0], [1, 3]]
=>
    x2  x4
r3  -1  12
r1   2  -1

But I get below:

>> df.loc["r2", ["x3", "x1"]]
Traceback (most recent call last):
        6: from /Users/mrkn/.rbenv/versions/2.7/bin/irb:23:in `<main>'
        5: from /Users/mrkn/.rbenv/versions/2.7/bin/irb:23:in `load'
        4: from /Users/mrkn/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/irb-1.2.3/exe/irb:11:in `<top (required)>'
        3: from (irb):145
        2: from /Users/mrkn/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/pycall-1.3.0/lib/pycall/pyobject_wrapper.rb:79:in `[]'
        1: from /Users/mrkn/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/pycall-1.3.0/lib/pycall/pyobject_wrapper.rb:79:in `getitem'
/Users/mrkn/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/pycall-1.3.0/lib/pycall/list.rb:18: warning: Capturing the given block using Kernel#proc is deprecated; use `&block` instead
PyCall::PyError (<class 'ValueError'>: No axis named 1 for object type <class 'pandas.core.series.Series'>)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexing.py", line 1762, in __getitem__
    return self._getitem_tuple(key)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexing.py", line 1289, in _getitem_tuple
    retval = getattr(retval, self.name)._getitem_axis(key, axis=i)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexing.py", line 1907, in _getitem_axis
    labels = self.obj._get_axis(axis)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/generic.py", line 423, in _get_axis
    name = self._get_axis_name(axis)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/generic.py", line 420, in _get_axis_name
    raise ValueError(f"No axis named {axis} for object type {cls}")

>> df.iloc[[2, 0], [1, 3]]
Traceback (most recent call last):
        7: from /Users/mrkn/.rbenv/versions/2.7/bin/irb:23:in `<main>'
        6: from /Users/mrkn/.rbenv/versions/2.7/bin/irb:23:in `load'
        5: from /Users/mrkn/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/irb-1.2.3/exe/irb:11:in `<top (required)>'
        4: from (irb):145
        3: from (irb):146:in `rescue in irb_binding'
        2: from /Users/mrkn/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/pycall-1.3.0/lib/pycall/pyobject_wrapper.rb:79:in `[]'
        1: from /Users/mrkn/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/pycall-1.3.0/lib/pycall/pyobject_wrapper.rb:79:in `getitem'
/Users/mrkn/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/pycall-1.3.0/lib/pycall/list.rb:18: warning: Capturing the given block using Kernel#proc is deprecated; use `&block` instead
PyCall::PyError (<class 'pandas.core.indexing.IndexingError'>: Too many indexers)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexing.py", line 1762, in __getitem__
    return self._getitem_tuple(key)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexing.py", line 2067, in _getitem_tuple
    self._has_valid_tuple(tup)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexing.py", line 703, in _has_valid_tuple
    self._validate_key(k, i)
  File "/opt/brew/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pandas/core/indexing.py", line 1998, in _validate_key
    raise IndexingError("Too many indexers")