remove ops div class to solve #21374 (#59144)

* remove core.computation.ops.Div resolves #21374 #58748

* need to preserve order

* updating tests

* update whatsnew

* solve mypy issue

* fixing pytests

* better than cast

* adding specific test

* Update pandas/tests/frame/test_query_eval.py

Co-authored-by: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>

* Update pandas/tests/computation/test_eval.py

Co-authored-by: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>

---------

Co-authored-by: Laurent Mutricy <laurent.mutricy@ekium.eu>
Co-authored-by: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>

doc/source/whatsnew/v3.0.0.rst

@@ -616,6 +616,7 @@ Other
 ^^^^^
 - Bug in :class:`DataFrame` when passing a ``dict`` with a NA scalar and ``columns`` that would always return ``np.nan`` (:issue:`57205`)
 - Bug in :func:`eval` on :class:`ExtensionArray` on including division ``/`` failed with a ``TypeError``. (:issue:`58748`)
+- Bug in :func:`eval` on :class:`complex` including division ``/`` discards imaginary part. (:issue:`21374`)
 - Bug in :func:`eval` where the names of the :class:`Series` were not preserved when using ``engine="numexpr"``. (:issue:`10239`)
 - Bug in :func:`unique` on :class:`Index` not always returning :class:`Index` (:issue:`57043`)
 - Bug in :meth:`DataFrame.apply` where passing ``engine="numba"`` ignored ``args`` passed to the applied function (:issue:`58712`)

pandas/_testing/__init__.py

@@ -107,6 +107,7 @@
 
 COMPLEX_DTYPES: list[Dtype] = [complex, "complex64", "complex128"]
 STRING_DTYPES: list[Dtype] = [str, "str", "U"]
+COMPLEX_FLOAT_DTYPES: list[Dtype] = [*COMPLEX_DTYPES, *FLOAT_NUMPY_DTYPES]
 
 DATETIME64_DTYPES: list[Dtype] = ["datetime64[ns]", "M8[ns]"]
 TIMEDELTA64_DTYPES: list[Dtype] = ["timedelta64[ns]", "m8[ns]"]

pandas/conftest.py

@@ -1448,6 +1448,21 @@ def complex_dtype(request):
     return request.param
 
 
+@pytest.fixture(params=tm.COMPLEX_FLOAT_DTYPES)
+def complex_or_float_dtype(request):
+    """
+    Parameterized fixture for complex and numpy float dtypes.
+
+    * complex
+    * 'complex64'
+    * 'complex128'
+    * float
+    * 'float32'
+    * 'float64'
+    """
+    return request.param
+
+
 @pytest.fixture(params=tm.SIGNED_INT_NUMPY_DTYPES)
 def any_signed_int_numpy_dtype(request):
     """

pandas/core/computation/expr.py

@@ -32,7 +32,6 @@
     UNARY_OPS_SYMS,
     BinOp,
     Constant,
-    Div,
     FuncNode,
     Op,
     Term,
@@ -374,7 +373,7 @@ class BaseExprVisitor(ast.NodeVisitor):
         "Add",
         "Sub",
         "Mult",
-        None,
+        "Div",
         "Pow",
         "FloorDiv",
         "Mod",
@@ -537,9 +536,6 @@ def visit_BinOp(self, node, **kwargs):
         left, right = self._maybe_downcast_constants(left, right)
         return self._maybe_evaluate_binop(op, op_class, left, right)
 
-    def visit_Div(self, node, **kwargs):
-        return lambda lhs, rhs: Div(lhs, rhs)
-
     def visit_UnaryOp(self, node, **kwargs):
         op = self.visit(node.op)
         operand = self.visit(node.operand)

pandas/core/computation/ops.py

@@ -18,7 +18,6 @@
 
 from pandas.core.dtypes.common import (
     is_list_like,
-    is_numeric_dtype,
     is_scalar,
 )
 
@@ -328,31 +327,6 @@ def _not_in(x, y):
     _binary_ops_dict.update(d)
 
 
-def _cast_inplace(terms, acceptable_dtypes, dtype) -> None:
-    """
-    Cast an expression inplace.
-
-    Parameters
-    ----------
-    terms : Op
-        The expression that should cast.
-    acceptable_dtypes : list of acceptable numpy.dtype
-        Will not cast if term's dtype in this list.
-    dtype : str or numpy.dtype
-        The dtype to cast to.
-    """
-    dt = np.dtype(dtype)
-    for term in terms:
-        if term.type in acceptable_dtypes:
-            continue
-
-        try:
-            new_value = term.value.astype(dt)
-        except AttributeError:
-            new_value = dt.type(term.value)
-        term.update(new_value)
-
-
 def is_term(obj) -> bool:
     return isinstance(obj, Term)
 
@@ -509,32 +483,6 @@ def _disallow_scalar_only_bool_ops(self) -> None:
             raise NotImplementedError("cannot evaluate scalar only bool ops")
 
 
-class Div(BinOp):
-    """
-    Div operator to special case casting.
-
-    Parameters
-    ----------
-    lhs, rhs : Term or Op
-        The Terms or Ops in the ``/`` expression.
-    """
-
-    def __init__(self, lhs, rhs) -> None:
-        super().__init__("/", lhs, rhs)
-
-        if not is_numeric_dtype(lhs.return_type) or not is_numeric_dtype(
-            rhs.return_type
-        ):
-            raise TypeError(
-                f"unsupported operand type(s) for {self.op}: "
-                f"'{lhs.return_type}' and '{rhs.return_type}'"
-            )
-
-        # do not upcast float32s to float64 un-necessarily
-        acceptable_dtypes = [np.float32, np.float64]
-        _cast_inplace(com.flatten(self), acceptable_dtypes, np.float64)
-
-
 UNARY_OPS_SYMS = ("+", "-", "~", "not")
 _unary_ops_funcs = (operator.pos, operator.neg, operator.invert, operator.invert)
 _unary_ops_dict = dict(zip(UNARY_OPS_SYMS, _unary_ops_funcs))

pandas/tests/computation/test_eval.py

@@ -758,16 +758,25 @@ class TestTypeCasting:
     # maybe someday... numexpr has too many upcasting rules now
     # chain(*(np.core.sctypes[x] for x in ['uint', 'int', 'float']))
     @pytest.mark.parametrize("left_right", [("df", "3"), ("3", "df")])
-    def test_binop_typecasting(self, engine, parser, op, float_numpy_dtype, left_right):
-        df = DataFrame(
-            np.random.default_rng(2).standard_normal((5, 3)), dtype=float_numpy_dtype
-        )
+    def test_binop_typecasting(
+        self, engine, parser, op, complex_or_float_dtype, left_right, request
+    ):
+        # GH#21374
+        dtype = complex_or_float_dtype
+        df = DataFrame(np.random.default_rng(2).standard_normal((5, 3)), dtype=dtype)
         left, right = left_right
         s = f"{left} {op} {right}"
         res = pd.eval(s, engine=engine, parser=parser)
-        assert df.values.dtype == float_numpy_dtype
-        assert res.values.dtype == float_numpy_dtype
-        tm.assert_frame_equal(res, eval(s))
+        if dtype == "complex64" and engine == "numexpr":
+            mark = pytest.mark.xfail(
+                reason="numexpr issue with complex that are upcast "
+                "to complex 128 "
+                "https://github.com/pydata/numexpr/issues/492"
+            )
+            request.applymarker(mark)
+        assert df.values.dtype == dtype
+        assert res.values.dtype == dtype
+        tm.assert_frame_equal(res, eval(s), check_exact=False)
 
 
 # -------------------------------------

pandas/tests/frame/test_query_eval.py

@@ -202,11 +202,23 @@ def test_eval_simple(self, engine, parser):
         expected = df["a"]
         tm.assert_series_equal(expected, res)
 
-    def test_extension_array_eval(self, engine, parser):
+    def test_extension_array_eval(self, engine, parser, request):
         # GH#58748
+        if engine == "numexpr":
+            mark = pytest.mark.xfail(
+                reason="numexpr does not support extension array dtypes"
+            )
+            request.applymarker(mark)
         df = DataFrame({"a": pd.array([1, 2, 3]), "b": pd.array([4, 5, 6])})
         result = df.eval("a / b", engine=engine, parser=parser)
-        expected = Series([0.25, 0.40, 0.50])
+        expected = Series(pd.array([0.25, 0.40, 0.50]))
+        tm.assert_series_equal(result, expected)
+
+    def test_complex_eval(self, engine, parser):
+        # GH#21374
+        df = DataFrame({"a": [1 + 2j], "b": [1 + 1j]})
+        result = df.eval("a/b", engine=engine, parser=parser)
+        expected = Series([1.5 + 0.5j])
         tm.assert_series_equal(result, expected)