Simplify transforms addition.

anntzer · anntzer · commit 2dabe851107a · 2020-01-07T23:39:59.000+01:00
- Suggest `tr1 + tr2` instead of `composite_transform_factory(tr1, tr2)`.
- No need to implement `Transform.__radd__` -- we can only add
  transforms so `__add__` is enough.
diff --git a/lib/matplotlib/projections/polar.py b/lib/matplotlib/projections/polar.py
@@ -820,9 +820,7 @@ def _set_lim_and_transforms(self):
             .scale(self._default_theta_direction, 1.0)
         self._theta_offset = mtransforms.Affine2D() \
             .translate(self._default_theta_offset, 0.0)
-        self.transShift = mtransforms.composite_transform_factory(
-            self._direction,
-            self._theta_offset)
+        self.transShift = self._direction + self._theta_offset
         # A view limit shifted to the correct location after accounting for
         # orientation and offset.
         self._realViewLim = mtransforms.TransformedBbox(self.viewLim,
diff --git a/lib/matplotlib/transforms.py b/lib/matplotlib/transforms.py
@@ -1243,23 +1243,11 @@ def __init_subclass__(cls):
 
     def __add__(self, other):
         """
-        Composes two transforms together such that *self* is followed
-        by *other*.
+        Compose two transforms together so that *self* is followed by *other*.
         """
-        if isinstance(other, Transform):
-            return composite_transform_factory(self, other)
-        raise TypeError(
-            "Can not add Transform to object of type '%s'" % type(other))
-
-    def __radd__(self, other):
-        """
-        Composes two transforms together such that *self* is followed
-        by *other*.
-        """
-        if isinstance(other, Transform):
-            return composite_transform_factory(other, self)
-        raise TypeError(
-            "Can not add Transform to object of type '%s'" % type(other))
+        return (composite_transform_factory(self, other)
+                if isinstance(other, Transform) else
+                NotImplemented)
 
     # Equality is based on object identity for `Transform`s (so we don't
     # override `__eq__`), but some subclasses, such as TransformWrapper &
@@ -2289,9 +2277,9 @@ def __init__(self, a, b, **kwargs):
         Create a new composite transform that is the result of
         applying transform *a* then transform *b*.
 
-        You will generally not call this constructor directly but use the
-        `composite_transform_factory` function instead, which can automatically
-        choose the best kind of composite transform instance to create.
+        You will generally not call this constructor directly but write ``a +
+        b`` instead, which will automatically choose the best kind of composite
+        transform instance to create.
         """
         if a.output_dims != b.input_dims:
             raise ValueError("The output dimension of 'a' must be equal to "
@@ -2405,13 +2393,11 @@ class CompositeAffine2D(Affine2DBase):
     def __init__(self, a, b, **kwargs):
         """
         Create a new composite transform that is the result of
-        applying transform *a* then transform *b*.
-
-        Both *a* and *b* must be instances of :class:`Affine2DBase`.
+        applying `Affine2DBase` *a* then `Affine2DBase` *b*.
 
-        You will generally not call this constructor directly but use the
-        `composite_transform_factory` function instead, which can automatically
-        choose the best kind of composite transform instance to create.
+        You will generally not call this constructor directly but write ``a +
+        b`` instead, which will automatically choose the best kind of composite
+        transform instance to create.
         """
         if not a.is_affine or not b.is_affine:
             raise ValueError("'a' and 'b' must be affine transforms")
