From 0a3c1d733e53be3d4c0e002f558c2fe0c3d647cf Mon Sep 17 00:00:00 2001
From: Souvik Mandal <mandalsouvik76@gmail.com>
Date: Fri, 27 Dec 2019 21:59:53 +0530
Subject: [PATCH] BUG: The setting xrot=0 in DataFrame.hist() doesn't work with
 by and subplots #30288 (#30491)

---
 doc/source/whatsnew/v1.0.0.rst            |  1 +
 pandas/plotting/_matplotlib/hist.py       |  3 ++-
 pandas/tests/plotting/test_hist_method.py | 18 ++++++++++++++++++
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/doc/source/whatsnew/v1.0.0.rst b/doc/source/whatsnew/v1.0.0.rst
index 284ce8bbecb67..0d0e9d9a54fff 100644
--- a/doc/source/whatsnew/v1.0.0.rst
+++ b/doc/source/whatsnew/v1.0.0.rst
@@ -828,6 +828,7 @@ Plotting
 - :func:`set_option` now validates that the plot backend provided to ``'plotting.backend'`` implements the backend when the option is set, rather than when a plot is created (:issue:`28163`)
 - :meth:`DataFrame.plot` now allow a ``backend`` keyword argument to allow changing between backends in one session (:issue:`28619`).
 - Bug in color validation incorrectly raising for non-color styles (:issue:`29122`).
+- Bug in :meth:`DataFrame.hist`, ``xrot=0`` does not work with ``by`` and subplots (:issue:`30288`).
 
 Groupby/resample/rolling
 ^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/pandas/plotting/_matplotlib/hist.py b/pandas/plotting/_matplotlib/hist.py
index 8957389ac2b13..f8b2c7ab123d0 100644
--- a/pandas/plotting/_matplotlib/hist.py
+++ b/pandas/plotting/_matplotlib/hist.py
@@ -250,7 +250,8 @@ def _grouped_hist(
     def plot_group(group, ax):
         ax.hist(group.dropna().values, bins=bins, **kwargs)
 
-    xrot = xrot or rot
+    if xrot is None:
+        xrot = rot
 
     fig, axes = _grouped_plot(
         plot_group,
diff --git a/pandas/tests/plotting/test_hist_method.py b/pandas/tests/plotting/test_hist_method.py
index 6c1c7dfd1a4a4..74d48c10ad9a0 100644
--- a/pandas/tests/plotting/test_hist_method.py
+++ b/pandas/tests/plotting/test_hist_method.py
@@ -253,6 +253,24 @@ def test_tight_layout(self):
 
         tm.close()
 
+    def test_hist_subplot_xrot(self):
+        # GH 30288
+        df = DataFrame(
+            {
+                "length": [1.5, 0.5, 1.2, 0.9, 3],
+                "animal": ["pig", "rabbit", "pig", "pig", "rabbit"],
+            }
+        )
+        axes = _check_plot_works(
+            df.hist,
+            filterwarnings="always",
+            column="length",
+            by="animal",
+            bins=5,
+            xrot=0,
+        )
+        self._check_ticks_props(axes, xrot=0)
+
 
 @td.skip_if_no_mpl
 class TestDataFrameGroupByPlots(TestPlotBase):