From c000643caa8e4bcdb9c064a783859a9921888502 Mon Sep 17 00:00:00 2001
From: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>
Date: Mon, 11 Jan 2021 23:12:52 +0100
Subject: [PATCH] Warn on redundant definition of plot properties
`plt.plot(x, y, fmt)` allows to specify marker, linestyle and color via
`fmt`. Warn if there are additionally keyword arguments that specify the
same properties.
Closes #19275.
---
examples/misc/svg_filter_line.py | 2 +-
lib/matplotlib/axes/_base.py | 26 ++++++++++++++++++++++++--
lib/matplotlib/tests/test_axes.py | 11 +++++++++++
3 files changed, 36 insertions(+), 3 deletions(-)
diff --git a/examples/misc/svg_filter_line.py b/examples/misc/svg_filter_line.py
index d4d42d2e7dca..d329e6f243b1 100644
--- a/examples/misc/svg_filter_line.py
+++ b/examples/misc/svg_filter_line.py
@@ -20,7 +20,7 @@
l1, = ax.plot([0.1, 0.5, 0.9], [0.1, 0.9, 0.5], "bo-",
mec="b", lw=5, ms=10, label="Line 1")
l2, = ax.plot([0.1, 0.5, 0.9], [0.5, 0.2, 0.7], "rs-",
- mec="r", lw=5, ms=10, color="r", label="Line 2")
+ mec="r", lw=5, ms=10, label="Line 2")
for l in [l1, l2]:
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
index cb6285c08d21..09d2a11b688e 100644
--- a/lib/matplotlib/axes/_base.py
+++ b/lib/matplotlib/axes/_base.py
@@ -117,6 +117,9 @@ def __call__(self, ax, renderer):
self._transform - ax.figure.transSubfigure)
+_FORMAT_UNSET = 'None'
+
+
def _process_plot_format(fmt):
"""
Convert a MATLAB style color/line style format string to a (*linestyle*,
@@ -129,6 +132,10 @@ def _process_plot_format(fmt):
* 'r--': red dashed lines
* 'C2--': the third color in the color cycle, dashed lines
+ The format is absolute in the sense that if a linestyle or marker is not
+ defined in *fmt*, there is no line or marker. This is expressed by
+ returning _FORMAT_UNSET for the respective quantity.
+
See Also
--------
matplotlib.Line2D.lineStyles, matplotlib.colors.cnames
@@ -196,9 +203,9 @@ def _process_plot_format(fmt):
if linestyle is None and marker is None:
linestyle = mpl.rcParams['lines.linestyle']
if linestyle is None:
- linestyle = 'None'
+ linestyle = _FORMAT_UNSET
if marker is None:
- marker = 'None'
+ marker = _FORMAT_UNSET
return linestyle, marker, color
@@ -461,6 +468,21 @@ def _plot_args(self, tup, kwargs, return_kwargs=False):
for prop_name, val in zip(('linestyle', 'marker', 'color'),
(linestyle, marker, color)):
if val is not None:
+ # check for conflicts between fmt and kwargs
+ if (fmt.lower() != 'none'
+ and prop_name in kwargs
+ and val != _FORMAT_UNSET):
+ # Technically ``plot(x, y, 'o', ls='--')`` is a conflict
+ # because 'o' implicitly unsets the linestyle
+ # (linestyle=_FORMAT_UNSET).
+ # We'll gracefully not warn in this case because an
+ # explicit set via kwargs can be seen as intention to
+ # override an implicit unset.
+ _api.warn_external(
+ f"{prop_name} is redundantly defined by the "
+ f"'{prop_name}' keyword argument and the fmt string "
+ f'"{fmt}" (-> {prop_name}={val!r}). The keyword '
+ f"argument will take precedence.")
kw[prop_name] = val
if len(xy) == 2:
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
index 2c57719481b9..2d448dd86d1a 100644
--- a/lib/matplotlib/tests/test_axes.py
+++ b/lib/matplotlib/tests/test_axes.py
@@ -624,6 +624,17 @@ def test_fill_units():
fig.autofmt_xdate()
+def test_plot_format_kwarg_redundant():
+ with pytest.warns(UserWarning, match="marker .* redundantly defined"):
+ plt.plot([0], [0], 'o', marker='x')
+ with pytest.warns(UserWarning, match="linestyle .* redundantly defined"):
+ plt.plot([0], [0], '-', linestyle='--')
+ with pytest.warns(UserWarning, match="color .* redundantly defined"):
+ plt.plot([0], [0], 'r', color='blue')
+ # smoke-test: should not warn
+ plt.errorbar([0], [0], fmt='none', color='blue')
+
+
@image_comparison(['single_point', 'single_point'])
def test_single_point():
# Issue #1796: don't let lines.marker affect the grid
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