Clarify the implementation of _process_plot_var_args.

anntzer · anntzer · commit d0d36cb6a9db · 2018-12-11T00:32:00.000+01:00
Having an argument named `kwargs` that's not a dict but a tuple is just
a good way to trip the reader.  Fortunately _getdefaults and
_setdefaults in only even called with a single kwargs, so we can replace
it with a single non-varargs argument and simplify the code at the same
time.
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -124,6 +124,11 @@ def _process_plot_format(fmt):
     return linestyle, marker, color
 
 
+def _no_none(d):
+    """Return the dict *d*, minus entries with a value of None."""
+    return {k: v for k, v in d.items() if v is not None}
+
+
 class _process_plot_var_args(object):
     """
     Process variable length arguments to the plot command, so that
@@ -235,27 +240,14 @@ def _xy_from_xy(self, x, y):
             y = y[:, np.newaxis]
         return x, y
 
-    def _getdefaults(self, ignore, *kwargs):
+    def _getdefaults(self, ignore, kw):
         """
-        Only advance the cycler if the cycler has information that
-        is not specified in any of the supplied tuple of dicts.
-        Ignore any keys specified in the `ignore` set.
-
-        Returns a copy of defaults dictionary if there are any
-        keys that are not found in any of the supplied dictionaries.
-        If the supplied dictionaries have non-None values for
-        everything the property cycler has, then just return
-        an empty dictionary. Ignored keys are excluded from the
-        returned dictionary.
-
+        If some keys in the property cycle (excluding those in the set
+        *ignore*) are absent or set to None in the dict *kw*, return a copy
+        of the next entry in the property cycle, excluding keys in *ignore*.
+        Otherwise, don't advance the property cycle, and return an empty dict.
         """
-        prop_keys = self._prop_keys
-        if ignore is None:
-            ignore = set()
-        prop_keys = prop_keys - ignore
-
-        if any(all(kw.get(k, None) is None for kw in kwargs)
-               for k in prop_keys):
+        if self._prop_keys - ignore - {*_no_none(kw)}:
             # Need to copy this dictionary or else the next time around
             # in the cycle, the dictionary could be missing entries.
             default_dict = next(self.prop_cycler).copy()
@@ -265,22 +257,10 @@ def _getdefaults(self, ignore, *kwargs):
             default_dict = {}
         return default_dict
 
-    def _setdefaults(self, defaults, *kwargs):
-        """
-        Given a defaults dictionary, and any other dictionaries,
-        update those other dictionaries with information in defaults if
-        none of the other dictionaries contains that information.
-
-        """
-        for k in defaults:
-            if all(kw.get(k, None) is None for kw in kwargs):
-                for kw in kwargs:
-                    kw[k] = defaults[k]
-
     def _makeline(self, x, y, kw, kwargs):
         kw = {**kw, **kwargs}  # Don't modify the original kw.
-        default_dict = self._getdefaults(None, kw)
-        self._setdefaults(default_dict, kw)
+        default_dict = self._getdefaults(set(), kw)
+        kw = {**default_dict, **_no_none(kw)}
         seg = mlines.Line2D(x, y, **kw)
         return seg
 
@@ -308,7 +288,7 @@ def _makefill(self, x, y, kw, kwargs):
         # Doing it with both seems to mess things up in
         # various places (probably due to logic bugs elsewhere).
         default_dict = self._getdefaults(ignores, kw)
-        self._setdefaults(default_dict, kw)
+        kw = {**default_dict, **_no_none(kw)}
 
         # Looks like we don't want "color" to be interpreted to
         # mean both facecolor and edgecolor for some reason.
@@ -323,7 +303,7 @@ def _makefill(self, x, y, kw, kwargs):
 
         # To get other properties set from the cycler
         # modify the kwargs dictionary.
-        self._setdefaults(default_dict, kwargs)
+        kwargs = {**default_dict, **_no_none(kwargs)}
 
         seg = mpatches.Polygon(np.column_stack((x, y)),
                                facecolor=facecolor,
@@ -391,8 +371,6 @@ def _grab_next_args(self, *args, **kwargs):
 
 
 class _AxesBase(martist.Artist):
-    """
-    """
     name = "rectilinear"
 
     _shared_x_axes = cbook.Grouper()
