Merge pull request matplotlib#21402 from DimitriPapadopoulos/argument_mutable_default

Do not use mutables as default parameters

Author: QuLogic

examples/images_contours_and_fields/image_annotated_heatmap.py

@@ -97,7 +97,7 @@
 
 
 def heatmap(data, row_labels, col_labels, ax=None,
-            cbar_kw={}, cbarlabel="", **kwargs):
+            cbar_kw=None, cbarlabel="", **kwargs):
     """
     Create a heatmap from a numpy array and two lists of labels.
 
@@ -120,9 +120,12 @@ def heatmap(data, row_labels, col_labels, ax=None,
         All other arguments are forwarded to `imshow`.
     """
 
-    if not ax:
+    if ax is None:
         ax = plt.gca()
 
+    if cbar_kw is None:
+        cbar_kw = {}
+
     # Plot the heatmap
     im = ax.imshow(data, **kwargs)
 

examples/widgets/annotated_cursor.py

@@ -76,7 +76,9 @@ class AnnotatedCursor(Cursor):
     """
 
     def __init__(self, line, numberformat="{0:.4g};{1:.4g}", offset=(5, 5),
-                 dataaxis='x', textprops={}, **cursorargs):
+                 dataaxis='x', textprops=None, **cursorargs):
+        if textprops is None:
+            textprops = {}
         # The line object, for which the coordinates are displayed
         self.line = line
         # The format string, on which .format() is called for creating the text

lib/matplotlib/backends/backend_svg.py

@@ -249,8 +249,8 @@ def flush(self):
         pass  # replaced by the constructor
 
 
-def generate_transform(transform_list=[]):
-    if len(transform_list):
+def generate_transform(transform_list=None):
+    if transform_list:
         output = StringIO()
         for type, value in transform_list:
             if (type == 'scale' and (value == (1,) or value == (1, 1))