API & BUG: allow list-like y argument to df.plot & fix integer arg to x,y

doc/source/whatsnew/v0.23.0.txt

@@ -965,6 +965,7 @@ Plotting
 ^^^^^^^^
 
 - :func:`DataFrame.plot` now raises a ``ValueError`` when the ``x`` or ``y`` argument is improperly formed (:issue:`18671`)
+- :func:`DataFrame.plot` now supports multiple columns to the ``y`` argument (:issue:`19699`)
 - Bug in formatting tick labels with ``datetime.time()`` and fractional seconds (:issue:`18478`).
 - :meth:`Series.plot.kde` has exposed the args ``ind`` and ``bw_method`` in the docstring (:issue:`18461`). The argument ``ind`` may now also be an integer (number of sample points).
 

pandas/plotting/_core.py

@@ -1714,13 +1714,28 @@ def _plot(data, x=None, y=None, subplots=False,
                 data = data.set_index(x)
 
             if y is not None:
-                if is_integer(y) and not data.columns.holds_integer():
+                int_cols = is_integer(y) or any(is_integer(col) for col in y)
+                if int_cols and not data.columns.holds_integer():
                     y = data.columns[y]
-                elif not isinstance(data[y], ABCSeries):
-                    raise ValueError("y must be a label or position")
-                label = kwds['label'] if 'label' in kwds else y
-                series = data[y].copy()  # Don't modify
-                series.name = label
+                elif not isinstance(data[y], (ABCSeries, ABCDataFrame)):
+                    raise ValueError(
+                        "y must be a label or position or list of them"
+                    )
+
+                label_kw = kwds['label'] if 'label' in kwds else False
+                new_data = data[y].copy()  # Don't modify
+
+                if isinstance(data[y], ABCSeries):
+                    label_name = label_kw or y
+                    new_data.name = label_name
+                else:
+                    match = is_list_like(label_kw) and len(label_kw) == len(y)
+                    if label_kw and not match:
+                        raise ValueError(
+                            "label should be list-like and same length as y"
+                        )
+                    label_name = label_kw or data[y].columns
+                    new_data.columns = label_name
 
                 for kw in ['xerr', 'yerr']:
                     if (kw in kwds) and \
@@ -1730,7 +1745,7 @@ def _plot(data, x=None, y=None, subplots=False,
                             kwds[kw] = data[kwds[kw]]
                         except (IndexError, KeyError, TypeError):
                             pass
-                data = series
+                data = new_data
         plot_obj = klass(data, subplots=subplots, ax=ax, kind=kind, **kwds)
 
     plot_obj.generate()
@@ -1743,7 +1758,7 @@ def _plot(data, x=None, y=None, subplots=False,
 series_kind = ""
 
 df_coord = """x : label or position, default None
-    y : label or position, default None
+    y : label, position or list of label, positions, default None
         Allows plotting of one column versus another"""
 series_coord = ""
 

pandas/tests/plotting/test_frame.py

@@ -2172,24 +2172,33 @@ def test_invalid_kind(self):
 
     @pytest.mark.parametrize("x,y", [
         (['B', 'C'], 'A'),
-        ('A', ['B', 'C'])
+        (['A'], ['B', 'C'])
     ])
     def test_invalid_xy_args(self, x, y):
-        # GH 18671
+        # GH 18671, 19699 allows y to be list-like but not x
         df = DataFrame({"A": [1, 2], 'B': [3, 4], 'C': [5, 6]})
         with pytest.raises(ValueError):
             df.plot(x=x, y=y)
 
     @pytest.mark.parametrize("x,y", [
         ('A', 'B'),
-        ('B', 'A')
+        (['A'], 'B')
     ])
     def test_invalid_xy_args_dup_cols(self, x, y):
-        # GH 18671
+        # GH 18671, 19699 allows y to be list-like but not x
         df = DataFrame([[1, 3, 5], [2, 4, 6]], columns=list('AAB'))
         with pytest.raises(ValueError):
             df.plot(x=x, y=y)
 
+    @pytest.mark.parametrize("y,lbl", [
+        (['B'], ['b']),
+        (['B', 'C'], ['b', 'c'])
+    ])
+    def test_y_listlike(self, y, lbl):
+        # GH 19699
+        df = DataFrame({"A": [1, 2], 'B': [3, 4], 'C': [5, 6]})
+        _check_plot_works(df.plot, x='A', y=y, label=lbl)
+
     @pytest.mark.slow
     def test_hexbin_basic(self):
         df = self.hexbin_df