matplotlib · efiring · Apr 21, 2019 · Apr 4, 2019
diff --git a/doc/api/next_api_changes/2019-04-16-AL.rst b/doc/api/next_api_changes/2019-04-16-AL.rst
@@ -0,0 +1,7 @@
+Deprecations
+````````````
+
+Returning a factor equal to None from axisartist Locators (which are **not**
+the same as "standard" tick Locators), or passing a factor equal to None
+to axisartist Formatters (which are **not** the same as "standard" tick
+Formatters) is deprecated.  Pass a factor equal to 1 instead.
diff --git a/lib/mpl_toolkits/axisartist/grid_finder.py b/lib/mpl_toolkits/axisartist/grid_finder.py
@@ -5,6 +5,16 @@
 from .clip_path import clip_line_to_rect


+def _deprecate_factor_none(factor):
+    # After the deprecation period, calls to _deprecate_factor_none can just be
+    # removed.
+    if factor is None:
+        cbook.warn_deprecated(
+            "3.2", "factor=None is deprecated; use/return factor=1 instead")
+        factor = 1
+    return factor
+
+
 # extremes finder
 class ExtremeFinderSimple(object):
    def __init__(self, nx, ny):
@@ -88,14 +98,8 @@ def get_grid_info(self, x1, y1, x2, y2):
        lon_levs, lon_n, lon_factor = self.grid_locator1(lon_min, lon_max)
        lat_levs, lat_n, lat_factor = self.grid_locator2(lat_min, lat_max)

-        if lon_factor is None:
-            lon_values = np.asarray(lon_levs[:lon_n])
-        else:
-            lon_values = np.asarray(lon_levs[:lon_n]/lon_factor)
-        if lat_factor is None:
-            lat_values = np.asarray(lat_levs[:lat_n])
-        else:
-            lat_values = np.asarray(lat_levs[:lat_n]/lat_factor)
+        lon_values = lon_levs[:lon_n] / _deprecate_factor_none(lon_factor)
+        lat_values = lat_levs[:lat_n] / _deprecate_factor_none(lat_factor)

        lon_lines, lat_lines = self._get_raw_grid_lines(lon_values,
                                                        lat_values,
@@ -226,37 +230,29 @@ def __init__(self, nbins=10, steps=None,
                                     integer=integer,
                                     symmetric=symmetric, prune=prune)
        self.create_dummy_axis()
-        self._factor = None
+        self._factor = 1

    def __call__(self, v1, v2):
-        if self._factor is not None:
-            self.set_bounds(v1*self._factor, v2*self._factor)
-            locs = mticker.MaxNLocator.__call__(self)
-            return np.array(locs), len(locs), self._factor
-        else:
-            self.set_bounds(v1, v2)
-            locs = mticker.MaxNLocator.__call__(self)
-            return np.array(locs), len(locs), None
+        self.set_bounds(v1 * self._factor, v2 * self._factor)
+        locs = mticker.MaxNLocator.__call__(self)
+        return np.array(locs), len(locs), self._factor

    def set_factor(self, f):
-        self._factor = f
+        self._factor = _deprecate_factor_none(f)


 class FixedLocator(object):
    def __init__(self, locs):
        self._locs = locs
-        self._factor = None
+        self._factor = 1

    def __call__(self, v1, v2):
-        if self._factor is None:
-            v1, v2 = sorted([v1, v2])
-        else:
-            v1, v2 = sorted([v1*self._factor, v2*self._factor])
+        v1, v2 = sorted([v1 * self._factor, v2 * self._factor])
        locs = np.array([l for l in self._locs if v1 <= l <= v2])
        return locs, len(locs), self._factor

    def set_factor(self, f):
-        self._factor = f
+        self._factor = _deprecate_factor_none(f)


 # Tick Formatter
@@ -270,9 +266,7 @@ def __init__(self, useMathText=True):

    def __call__(self, direction, factor, values):
        if not self._ignore_factor:
-            if factor is None:
-                factor = 1
-            values = [v / factor for v in values]
+            values = [v / _deprecate_factor_none(factor) for v in values]
        return self._fmt.format_ticks(values)


@@ -290,13 +284,10 @@ def __call__(self, direction, factor, values):
        """
        factor is ignored if value is found in the dictionary
        """
-
        if self._fallback_formatter:
            fallback_strings = self._fallback_formatter(
                direction, factor, values)
        else:
-            fallback_strings = [""]*len(values)
-
-        r = [self._format_dict.get(k, v) for k, v in zip(values,
-                                                         fallback_strings)]
-        return r
+            fallback_strings = [""] * len(values)
+        return [self._format_dict.get(k, v)
+                for k, v in zip(values, fallback_strings)]
diff --git a/lib/mpl_toolkits/axisartist/grid_helper_curvelinear.py b/lib/mpl_toolkits/axisartist/grid_helper_curvelinear.py
@@ -9,7 +9,7 @@
 from matplotlib.transforms import Affine2D, IdentityTransform
 from .axislines import AxisArtistHelper, GridHelperBase
 from .axis_artist import AxisArtist
-from .grid_finder import GridFinder
+from .grid_finder import GridFinder, _deprecate_factor_none


 class FixedAxisArtistHelper(AxisArtistHelper.Fixed):
@@ -132,12 +132,12 @@ def update_lim(self, axes):

        self.grid_info = {
            "extremes": extremes,
-            "lon_info": (lon_levs, lon_n, lon_factor),
-            "lat_info": (lat_levs, lat_n, lat_factor),
+            "lon_info": (lon_levs, lon_n, _deprecate_factor_none(lon_factor)),
+            "lat_info": (lat_levs, lat_n, _deprecate_factor_none(lat_factor)),
            "lon_labels": grid_finder.tick_formatter1(
-                "bottom", lon_factor, lon_levs),
+                "bottom", _deprecate_factor_none(lon_factor), lon_levs),
            "lat_labels": grid_finder.tick_formatter2(
-                "bottom", lat_factor, lat_levs),
+                "bottom", _deprecate_factor_none(lat_factor), lat_levs),
            "line_xy": (xx, yy),
        }

@@ -183,21 +183,13 @@ def get_tick_iterators(self, axes):

        lat_levs, lat_n, lat_factor = self.grid_info["lat_info"]
        lat_levs = np.asarray(lat_levs)
-        if lat_factor is not None:
-            yy0 = lat_levs / lat_factor
-            dy = 0.01 / lat_factor
-        else:
-            yy0 = lat_levs
-            dy = 0.01
+        yy0 = lat_levs / _deprecate_factor_none(lat_factor)
+        dy = 0.01 / _deprecate_factor_none(lat_factor)

        lon_levs, lon_n, lon_factor = self.grid_info["lon_info"]
        lon_levs = np.asarray(lon_levs)
-        if lon_factor is not None:
-            xx0 = lon_levs / lon_factor
-            dx = 0.01 / lon_factor
-        else:
-            xx0 = lon_levs
-            dx = 0.01
+        xx0 = lon_levs / _deprecate_factor_none(lon_factor)
+        dx = 0.01 / _deprecate_factor_none(lon_factor)

        if None in self._extremes:
            e0, e1 = self._extremes