Do not overwrite labels set with labs

... unless if using labs to overwrite.

Author: has2k1

doc/changelog.qmd

@@ -1,6 +1,23 @@
 ---
 title: Changelog
 ---
+
+## v0.15.1
+(not-yet-released)
+
+### Bug Fixes
+
+- Fixed labels set with the `labs` call so that they are only ever overwritten
+  by a call to `labs` or setting the `name` of a scale. Previously, if a
+  global mapping was added after `labs`, it over-wrote the previously set labels.
+
+  ```python
+  ggplot(mtcars) + labs(x="x title", y="y title") + geom_point() + aes("wt", "mpg")
+  ```
+
+  The labels will be "x title" and "y title".
+
+
 ## v0.15.0
 
 (2025-06-15)

plotnine/ggplot.py

@@ -36,9 +36,9 @@
 from .facets.layout import Layout
 from .geoms.geom_blank import geom_blank
 from .guides.guides import guides
-from .iapi import mpl_save_view
+from .iapi import labels_view, mpl_save_view
 from .layer import Layers
-from .mapping.aes import aes, make_labels
+from .mapping.aes import aes
 from .options import get_option
 from .scales.scales import Scales
 from .themes.theme import theme, theme_get
@@ -55,7 +55,6 @@
     from plotnine.composition import Compose
     from plotnine.coords.coord import coord
     from plotnine.facets.facet import facet
-    from plotnine.layer import layer
     from plotnine.typing import DataLike
 
     class PlotAddable(Protocol):
@@ -118,7 +117,7 @@ def __init__(
         self.data = data
         self.mapping = mapping if mapping is not None else aes()
         self.facet: facet = facet_null()
-        self.labels = make_labels(self.mapping)
+        self.labels = labels_view()
         self.layers = Layers()
         self.guides = guides()
         self.scales = Scales()
@@ -301,10 +300,7 @@ def draw(self, *, show: bool = False) -> Figure:
         from ._mpl.layout_manager import PlotnineLayoutEngine
 
         with plot_context(self, show=show):
-            if not hasattr(self, "figure"):
-                self._create_figure()
-            figure = self.figure
-
+            figure = self._setup()
             self._build()
 
             # setup
@@ -327,6 +323,16 @@ def draw(self, *, show: bool = False) -> Figure:
 
         return figure
 
+    def _setup(self) -> Figure:
+        """
+        Setup this instance for the building process
+        """
+        if not hasattr(self, "figure"):
+            self._create_figure()
+
+        self.labels.add_defaults(self.mapping.labels)
+        return self.figure
+
     def _create_figure(self):
         """
         Create gridspec for the panels
@@ -548,21 +554,6 @@ def _save_filename(self, ext: str) -> Path:
         hash_token = abs(self.__hash__())
         return Path(f"plotnine-save-{hash_token}.{ext}")
 
-    def _update_labels(self, layer: layer):
-        """
-        Update label data for the ggplot
-
-        Parameters
-        ----------
-        layer : layer
-            New layer that has just been added to the ggplot
-            object.
-        """
-        mapping = make_labels(layer.mapping)
-        default = make_labels(layer.stat.DEFAULT_AES)
-        mapping.add_defaults(default)
-        self.labels.add_defaults(mapping)
-
     def save_helper(
         self: ggplot,
         filename: Optional[str | Path | BytesIO] = None,

plotnine/layer.py

@@ -8,7 +8,7 @@
 
 from ._utils import array_kind, check_required_aesthetics, ninteraction
 from .exceptions import PlotnineError
-from .mapping.aes import NO_GROUP, SCALED_AESTHETICS, aes
+from .mapping.aes import NO_GROUP, SCALED_AESTHETICS, aes, make_labels
 from .mapping.evaluation import evaluate, stage
 
 if typing.TYPE_CHECKING:
@@ -409,6 +409,13 @@ def finish_statistics(self):
         """
         self.stat.finish_layer(self.data)
 
+    def update_labels(self, plot: ggplot):
+        """
+        Update label data for the ggplot from the mappings in this layer
+        """
+        plot.labels.add_defaults(self.mapping.labels)
+        plot.labels.add_defaults(make_labels(self.stat.DEFAULT_AES))
+
 
 class Layers(List[layer]):
     """
@@ -509,7 +516,7 @@ def finish_statistics(self):
 
     def update_labels(self, plot: ggplot):
         for l in self:
-            plot._update_labels(l)
+            l.update_labels(plot)
 
 
 def add_group(data: pd.DataFrame) -> pd.DataFrame:

plotnine/mapping/aes.py

@@ -290,9 +290,15 @@ def __radd__(self, other):
         """
         self = deepcopy(self)
         other.mapping.update(self)
-        other.labels.update(make_labels(self))
         return other
 
+    @property
+    def labels(self) -> labels_view:
+        """
+        The labels for this mapping
+        """
+        return make_labels(self)
+
     def copy(self):
         return aes(**self)
 

tests/test_aes.py

@@ -9,6 +9,7 @@
     geom_crossbar,
     geom_point,
     ggplot,
+    labs,
     scale_x_log10,
     scale_y_log10,
     stage,
@@ -26,14 +27,6 @@
 )
 
 
-data = pd.DataFrame(
-    {
-        "x": pd.Categorical(["b", "d", "c", "a"], ordered=True),
-        "y": [1, 2, 3, 4],
-    }
-)
-
-
 def test_reorder():
     p = (
         ggplot(data, aes("reorder(x, y)", "y", fill="reorder(x, y)"))
@@ -50,15 +43,17 @@ def test_reorder_index():
 
 
 def test_labels_series():
-    p = ggplot(data, aes(x=data.x, y=data.y)) + geom_col()
+    p = ggplot(data, aes(x=data.x, y=data.y)) + geom_col() + labs(y="yy")
+    p.draw()
     assert p.labels.x == "x"
-    assert p.labels.y == "y"
+    assert p.labels.y == "yy"
 
 
 def test_labels_lists():
-    p = ggplot(data, aes(x=[1, 2, 3], y=[1, 2, 3])) + geom_col()
-    assert p.labels.x is None
-    assert p.labels.y is None
+    p = ggplot(data, aes(x=[0, 1, 2, 3], y=range(4))) + geom_col()
+    p.draw()
+    assert p.labels.x == ""
+    assert p.labels.y == ""
 
 
 def test_irregular_shapes():

tests/test_ggplot_internals.py

@@ -222,12 +222,21 @@ def test_add_aes():
     data = pd.DataFrame({"var1": [1, 2, 3, 4], "var2": 2})
     p = ggplot(data) + geom_point()
     p += aes("var1", "var2")
-
+    p.draw()
     assert p.mapping == aes("var1", "var2")
     assert p.labels.x == "var1"
     assert p.labels.y == "var2"
 
 
+def test_add_labs():
+    data = pd.DataFrame({"var1": [1, 2, 3, 4], "var2": 2})
+    p = ggplot(data) + geom_point() + labs(x="x title")
+    p += aes("var1", "var2")
+    p.draw()
+    assert p.labels.x == "x title"
+    assert p.labels.y == "var2"
+
+
 def test_nonzero_indexed_data():
     data = pd.DataFrame(
         {98: {"blip": 0, "blop": 1}, 99: {"blip": 1, "blop": 3}}