diff --git a/doc/conf.py b/doc/conf.py
index 592b349ca104..d92366401287 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -118,7 +118,7 @@
 plot_formats = [('png', 80), ('hires.png', 200), ('pdf', 50)]
 
 # Subdirectories in 'examples/' directory of package and titles for gallery
-mpl_example_sections = (
+mpl_example_sections = [
     ('lines_bars_and_markers', 'Lines, bars, and markers'),
     ('shapes_and_collections', 'Shapes and collections'),
     ('statistics', 'Statistical plots'),
@@ -138,7 +138,7 @@
     ('axes_grid', 'axes_grid toolkit'),
     ('units', 'units'),
     ('widgets', 'widgets'),
-    )
+    ]
 
 
 # Github extension
diff --git a/lib/matplotlib/sphinxext/mathmpl.py b/lib/matplotlib/sphinxext/mathmpl.py
index f44c1d75625a..8fc7ed2b3d2e 100644
--- a/lib/matplotlib/sphinxext/mathmpl.py
+++ b/lib/matplotlib/sphinxext/mathmpl.py
@@ -87,16 +87,15 @@ def latex2html(node, source):
 
     return '<img src="%s/%s.png" %s%s/>' % (path, name, cls, style)
 
+
 def setup(app):
     setup.app = app
 
-    app.add_node(latex_math)
-    app.add_role('math', math_role)
-
     # Add visit/depart methods to HTML-Translator:
     def visit_latex_math_html(self, node):
         source = self.document.attributes['source']
         self.body.append(latex2html(node, source))
+
     def depart_latex_math_html(self, node):
         pass
 
@@ -109,13 +108,13 @@ def visit_latex_math_latex(self, node):
             self.body.extend(['\\begin{equation}',
                               node['latex'],
                               '\\end{equation}'])
+
     def depart_latex_math_latex(self, node):
         pass
 
-    app.add_node(latex_math, html=(visit_latex_math_html,
-                                   depart_latex_math_html))
-    app.add_node(latex_math, latex=(visit_latex_math_latex,
-                                    depart_latex_math_latex))
+    app.add_node(latex_math,
+                 html=(visit_latex_math_html, depart_latex_math_html),
+                 latex=(visit_latex_math_latex, depart_latex_math_latex))
     app.add_role('math', math_role)
     app.add_directive('math', math_directive,
                       True, (0, 0, 0), **options_spec)
diff --git a/lib/matplotlib/sphinxext/only_directives.py b/lib/matplotlib/sphinxext/only_directives.py
index fdc8000ab9b1..05b99b38ffb4 100644
--- a/lib/matplotlib/sphinxext/only_directives.py
+++ b/lib/matplotlib/sphinxext/only_directives.py
@@ -41,11 +41,10 @@ def builder_inited(app):
     else:
         html_only.traverse = only_base.dont_traverse
 
+
 def setup(app):
     app.add_directive('htmlonly', html_only_directive, True, (0, 0, 0))
     app.add_directive('latexonly', latex_only_directive, True, (0, 0, 0))
-    app.add_node(html_only)
-    app.add_node(latex_only)
 
     # This will *really* never see the light of day As it turns out,
     # this results in "broken" image nodes since they never get
@@ -55,14 +54,19 @@ def setup(app):
     # Add visit/depart methods to HTML-Translator:
     def visit_perform(self, node):
         pass
+
     def depart_perform(self, node):
         pass
+
     def visit_ignore(self, node):
         node.children = []
+
     def depart_ignore(self, node):
         node.children = []
 
-    app.add_node(html_only, html=(visit_perform, depart_perform))
-    app.add_node(html_only, latex=(visit_ignore, depart_ignore))
-    app.add_node(latex_only, latex=(visit_perform, depart_perform))
-    app.add_node(latex_only, html=(visit_ignore, depart_ignore))
+    app.add_node(html_only,
+                 html=(visit_perform, depart_perform),
+                 latex=(visit_ignore, depart_ignore))
+    app.add_node(latex_only,
+                 latex=(visit_perform, depart_perform),
+                 html=(visit_ignore, depart_ignore))