Set axis linecolor to black by default when converting from matplotlib figure

Author: robertoffmoura

plotly/matplotlylib/renderer.py

@@ -154,10 +154,10 @@ def open_axes(self, ax, props):
         self.axis_ct += 1
         # set defaults in axes
         xaxis = go.layout.XAxis(
-            anchor="y{0}".format(self.axis_ct), zeroline=False, ticks="inside"
+            anchor="y{0}".format(self.axis_ct), zeroline=False, ticks="inside", linecolor="black"
         )
         yaxis = go.layout.YAxis(
-            anchor="x{0}".format(self.axis_ct), zeroline=False, ticks="inside"
+            anchor="x{0}".format(self.axis_ct), zeroline=False, ticks="inside", linecolor="black"
         )
         # update defaults with things set in mpl
         mpl_xaxis, mpl_yaxis = mpltools.prep_xy_axis(

plotly/matplotlylib/tests/test_renderer.py

@@ -84,3 +84,13 @@ def test_multiple_traces_native_legend():
     assert plotly_fig.data[0].mode == "lines"
     assert plotly_fig.data[1].mode == "markers"
     assert plotly_fig.data[2].mode == "lines+markers"
+
+
+def test_axis_linecolor_defaults_to_black():
+    fig, ax = plt.subplots()
+    ax.plot([0, 1], [0, 1])
+
+    plotly_fig = tls.mpl_to_plotly(fig)
+
+    assert plotly_fig.layout.xaxis.linecolor == "black"
+    assert plotly_fig.layout.yaxis.linecolor == "black"