Merge pull request pandas-dev#4966 from cpcloud/scatter-matrix-kwargs

CLN: do not use mutable default arguments

Author: cpcloud

pandas/tools/plotting.py

@@ -201,8 +201,8 @@ def use(self, key, value):
 
 
 def scatter_matrix(frame, alpha=0.5, figsize=None, ax=None, grid=False,
-                   diagonal='hist', marker='.', density_kwds={}, hist_kwds={},
-                   **kwds):
+                   diagonal='hist', marker='.', density_kwds=None,
+                   hist_kwds=None, **kwds):
     """
     Draw a matrix of scatter plots.
 
@@ -243,6 +243,9 @@ def scatter_matrix(frame, alpha=0.5, figsize=None, ax=None, grid=False,
 
     marker = _get_marker_compat(marker)
 
+    hist_kwds = hist_kwds or {}
+    density_kwds = density_kwds or {}
+
     for i, a in zip(lrange(n), df.columns):
         for j, b in zip(lrange(n), df.columns):
             ax = axes[i, j]