fix issue

pint_pandas/pint_array.py

@@ -214,19 +214,18 @@ def _get_common_dtype(self, dtypes):
  -------
  returns self for acceptable cases or None otherwise
  """
+ # Return self (PintType with same units) if possible
  if all(
- isinstance(x, PintType) or pd.api.types.is_numeric_dtype(x) for x in dtypes
+ isinstance(dtype, PintType) and dtype.units == self.units
+ for dtype in dtypes
  ):
- PintType_list = [x for x in dtypes if isinstance(x, PintType)]
- if len(PintType_list) < 2:
- return self
- if all(
- PintType_list[0].units.is_compatible_with(x.units)
- for x in PintType_list[1:]
- ):
- return self
- else:
- return None
+ return self
+ # Otherwise return PintType with undefined units
+ elif all(
+ isinstance(dtype, PintType) or pd.api.types.is_numeric_dtype(dtype)
+ for dtype in dtypes
+ ):
+ return PintType
  else:
  return None
 

pint_pandas/testsuite/test_issues.py

@@ -277,6 +277,7 @@ def test_eval(self):
  )
  tm.assert_series_equal(df.eval("a / b"), df["a"] / df["b"])
  tm.assert_series_equal(df.eval("a / c"), df["a"] / df["c"])
+ tm.assert_series_equal(df.eval("a / a"), df["a"] / df["a"])
 
  def test_mixed_df(self):
  df = pd.DataFrame(
@@ -287,4 +288,26 @@ def test_mixed_df(self):
  }
  )
 
- assert df["a"][0] == df.iloc[0][0]
+ assert df["a"][0] == df.iloc[0, 0]
+
+
+class TestIssue246(BaseExtensionTests):
+ def test_issue246(self):
+ df = pd.DataFrame(
+ {
+ "a": [1, 2, 3],
+ "b": [4, 5, 6],
+ "c": [7, 8, 9],
+ }
+ )
+
+ df = df.astype(
+ {
+ "a": "pint[m]",
+ "b": "pint[m/s]",
+ "c": "pint[kN]",
+ }
+ )
+
+ # now an operation where each cell is independent from each other
+ df.apply(lambda x: x * 2, axis=1)