Fix facet_col and animation_frame in px.imshow for xarrays.

CHANGELOG.md

@@ -2,6 +2,9 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
+## UNRELEASED
+ - Fixed two issues with px.imshow: [#4330] when facet_col is an earlier dimension than animation_frame for xarrays and [#4329] when facet_col has string coordinates in xarrays [#4331]
+
 ## [5.16.1] - 2023-08-16
 
 ### Fixed

packages/python/plotly/plotly/express/_imshow.py

@@ -265,14 +265,18 @@ def imshow(
     if xarray_imported and isinstance(img, xarray.DataArray):
         dims = list(img.dims)
         img_is_xarray = True
+        pop_indexes = []
         if facet_col is not None:
             facet_slices = img.coords[img.dims[facet_col]].values
-            _ = dims.pop(facet_col)
+            pop_indexes.append(facet_col)
             facet_label = img.dims[facet_col]
         if animation_frame is not None:
             animation_slices = img.coords[img.dims[animation_frame]].values
-            _ = dims.pop(animation_frame)
+            pop_indexes.append(animation_frame)
             animation_label = img.dims[animation_frame]
+        # Remove indices in sorted order.
+        for index in sorted(pop_indexes, reverse=True):
+            _ = dims.pop(index)
         y_label, x_label = dims[0], dims[1]
         # np.datetime64 is not handled correctly by go.Heatmap
         for ax in [x_label, y_label]:
@@ -541,7 +545,7 @@ def imshow(
         slice_label = (
             "facet_col" if labels.get("facet_col") is None else labels["facet_col"]
         )
-        col_labels = ["%s=%d" % (slice_label, i) for i in facet_slices]
+        col_labels = [f"{slice_label}={i}" for i in facet_slices]
     fig = init_figure(args, "xy", [], nrows, ncols, col_labels, [])
     for attr_name in ["height", "width"]:
         if args[attr_name]:

packages/python/plotly/plotly/tests/test_optional/test_px/test_imshow.py

@@ -194,6 +194,40 @@ def test_imshow_xarray_slicethrough():
     assert np.all(np.array(fig.data[0].x) == np.array(da.coords["dim_2"]))
 
 
+def test_imshow_xarray_facet_col_string():
+    img = np.random.random((3, 4, 5))
+    da = xr.DataArray(
+        img, dims=["str_dim", "dim_1", "dim_2"], coords={"str_dim": ["A", "B", "C"]}
+    )
+    fig = px.imshow(da, facet_col="str_dim")
+    # Dimensions are used for axis labels and coordinates
+    assert fig.layout.xaxis.title.text == "dim_2"
+    assert fig.layout.yaxis.title.text == "dim_1"
+    assert np.all(np.array(fig.data[0].x) == np.array(da.coords["dim_2"]))
+
+
+def test_imshow_xarray_animation_frame_string():
+    img = np.random.random((3, 4, 5))
+    da = xr.DataArray(
+        img, dims=["str_dim", "dim_1", "dim_2"], coords={"str_dim": ["A", "B", "C"]}
+    )
+    fig = px.imshow(da, animation_frame="str_dim")
+    # Dimensions are used for axis labels and coordinates
+    assert fig.layout.xaxis.title.text == "dim_2"
+    assert fig.layout.yaxis.title.text == "dim_1"
+    assert np.all(np.array(fig.data[0].x) == np.array(da.coords["dim_2"]))
+
+
+def test_imshow_xarray_animation_facet_slicethrough():
+    img = np.random.random((3, 4, 5, 6))
+    da = xr.DataArray(img, dims=["dim_0", "dim_1", "dim_2", "dim_3"])
+    fig = px.imshow(da, facet_col="dim_0", animation_frame="dim_1")
+    # Dimensions are used for axis labels and coordinates
+    assert fig.layout.xaxis.title.text == "dim_3"
+    assert fig.layout.yaxis.title.text == "dim_2"
+    assert np.all(np.array(fig.data[0].x) == np.array(da.coords["dim_3"]))
+
+
 def test_imshow_labels_and_ranges():
     fig = px.imshow(
         [[1, 2], [3, 4], [5, 6]],