BUG: column names with degree sign make query fail (pandas-dev#42826)

Author: fdion

doc/source/whatsnew/v1.4.0.rst

@@ -234,6 +234,8 @@ Indexing
 - Bug in indexing on a :class:`MultiIndex` failing to drop scalar levels when the indexer is a tuple containing a datetime-like string (:issue:`42476`)
 - Bug in :meth:`DataFrame.sort_values` and :meth:`Series.sort_values` when passing an ascending value, failed to raise or incorrectly raising ``ValueError`` (:issue:`41634`)
 - Bug in updating values of :class:`pandas.Series` using boolean index, created by using :meth:`pandas.DataFrame.pop` (:issue:`42530`)
+- Bug in :meth:`DataFrame.query` did not handle the degree sign in a backticked column name, such as \`Temp(°C)\`, used in an expression to query a dataframe (:issue:`42826`)
+-
 
 Missing
 ^^^^^^^

pandas/core/computation/parsing.py

@@ -49,6 +49,7 @@ def create_valid_python_identifier(name: str) -> str:
             "!": "_EXCLAMATIONMARK_",
             "$": "_DOLLARSIGN_",
             "€": "_EUROSIGN_",
+            "°": "_DEGREESIGN_",
             # Including quotes works, but there are exceptions.
             "'": "_SINGLEQUOTE_",
             '"': "_DOUBLEQUOTE_",

pandas/tests/computation/test_eval.py

@@ -2035,6 +2035,16 @@ def test_truediv_deprecated(engine, parser):
     assert match in str(m[0].message)
 
 
+@pytest.mark.parametrize("column", ["Temp(°C)", "Capacitance(μF)"])
+def test_query_token(engine, column):
+    # See: https://github.com/pandas-dev/pandas/pull/42826
+    df = DataFrame(np.random.randn(5, 2), columns=[column, "b"])
+    expected = df[df[column] > 5]
+    query_string = f"`{column}` > 5"
+    result = df.query(query_string, engine=engine)
+    tm.assert_frame_equal(result, expected)
+
+
 def test_negate_lt_eq_le(engine, parser):
     df = DataFrame([[0, 10], [1, 20]], columns=["cat", "count"])
     expected = df[~(df.cat > 0)]