Add simple polars support (#1129)

Co-authored-by: maximlt <mliquet@anaconda.com>
Co-authored-by: Maxime Liquet <35924738+maximlt@users.noreply.github.com>

doc/index.md

@@ -101,6 +101,20 @@ alt: Works with GeoPandas
 align: center
 ---
 :::
+:::{tab-item} Polars
+```python
+import polars
+import hvplot.polars
+
+df_polars = polars.from_pandas(df)
+df_polars.hvplot.scatter(x='bill_length_mm', y='bill_depth_mm', by='species')
+```
+```{image} ./_static/home/dask.gif
+---
+alt: Works with Polars
+align: center
+---
+:::
 
 :::{tab-item} Intake
 ```python

examples/user_guide/Introduction.ipynb

@@ -8,6 +8,7 @@
     "\n",
     "* [Pandas](https://pandas.pydata.org): DataFrame, Series (columnar/tabular data)\n",
     "* [Rapids cuDF](https://docs.rapids.ai/api/cudf/stable/): GPU DataFrame, Series (columnar/tabular data)\n",
+    "* [Polars](https://www.pola.rs/): Polars is a fast DataFrame library/in-memory query engine (columnar/tabular data)\n",
     "* [Dask](https://www.dask.org): DataFrame, Series (distributed/out of core arrays and columnar data)\n",
     "* [XArray](https://xarray.pydata.org): Dataset, DataArray (labelled multidimensional arrays)\n",
     "* [Streamz](https://streamz.readthedocs.io): DataFrame(s), Series(s) (streaming columnar data)\n",

hvplot/polars.py

@@ -0,0 +1,64 @@
+"""Adds the `.hvplot` method to pl.DataFrame, pl.LazyFrame and pl.Series"""
+import itertools
+
+from hvplot import hvPlotTabular, post_patch
+from hvplot.converter import HoloViewsConverter
+from hvplot.util import is_list_like
+
+
+class hvPlotTabularPolars(hvPlotTabular):
+    def _get_converter(self, x=None, y=None, kind=None, **kwds):
+        import polars as pl
+
+        params = dict(self._metadata, **kwds)
+        x = x or params.pop("x", None)
+        y = y or params.pop("y", None)
+        kind = kind or params.pop("kind", None)
+
+        # Find columns which should be converted for LazyDataFrame and DataFrame
+        if isinstance(self._data, (pl.LazyFrame, pl.DataFrame)):
+            if params.get("hover_cols") == "all":
+                columns = list(self._data.columns)
+            else:
+                possible_columns = [
+                    [v] if isinstance(v, str) else v
+                    for v in params.values()
+                    if isinstance(v, (str, list))
+                ]
+                columns = (
+                    set(self._data.columns) & set(itertools.chain(*possible_columns))
+                ) or {self._data.columns[0]}
+                xs = x if is_list_like(x) else (x,)
+                ys = y if is_list_like(y) else (y,)
+                columns |= {*xs, *ys}
+                columns.discard(None)
+
+        if isinstance(self._data, pl.DataFrame):
+            data = self._data.select(columns).to_pandas()
+        elif isinstance(self._data, pl.Series):
+            data = self._data.to_pandas()
+        elif isinstance(self._data, pl.LazyFrame):
+            data = self._data.select(columns).collect().to_pandas()
+        else:
+            raise ValueError(
+                "Only Polars DataFrame, Series, and LazyFrame are supported"
+            )
+
+        return HoloViewsConverter(data, x, y, kind=kind, **params)
+
+
+def patch(name="hvplot", extension="bokeh", logo=False):
+    try:
+        import polars as pl
+    except:
+        raise ImportError(
+            "Could not patch plotting API onto Polars. Polars could not be imported."
+        )
+    pl.api.register_dataframe_namespace(name)(hvPlotTabularPolars)
+    pl.api.register_series_namespace(name)(hvPlotTabularPolars)
+    pl.api.register_lazyframe_namespace(name)(hvPlotTabularPolars)
+
+    post_patch(extension, logo)
+
+
+patch()

hvplot/tests/plotting/testcore.py

@@ -1,21 +1,66 @@
 import numpy as np
 import pandas as pd
 import hvplot.pandas  # noqa
-
 import pytest
 
-@pytest.mark.parametrize("y", (
+from hvplot import hvPlotTabular
+
+try:
+    import polars as pl
+    import hvplot.polars  # noqa
+    skip_polar = False
+except ImportError:
+    class pl:
+        DataFrame = None
+        LazyFrame = None
+        Series = None
+    skip_polar = True
+
+
+TYPES = {t for t in dir(hvPlotTabular) if not t.startswith("_")}
+FRAME_TYPES = TYPES - {"bivariate", "heatmap", "hexbin", "labels", "vectorfield"}
+SERIES_TYPES = FRAME_TYPES - {"points", "polygons", "ohlc", "paths"}
+frame_kinds = pytest.mark.parametrize("kind", FRAME_TYPES)
+series_kinds = pytest.mark.parametrize("kind", SERIES_TYPES)
+
+y_combinations = pytest.mark.parametrize("y", (
     ["A", "B", "C", "D"],
     ("A", "B", "C", "D"),
     {"A", "B", "C", "D"},
     np.array(["A", "B", "C", "D"]),
     pd.Index(["A", "B", "C", "D"]),
     pd.Series(["A", "B", "C", "D"]),
-    ))
-def test_diffent_input_types(y):
+    ),
+    ids=lambda x: type(x).__name__
+)
+
+
+@frame_kinds
+@y_combinations
+def test_dataframe_pandas(kind, y):
     df = pd._testing.makeDataFrame()
-    types = {t for t in dir(df.hvplot) if not t.startswith("_")}
-    ignore_types = {'bivariate', 'heatmap', 'hexbin', 'labels', 'vectorfield'}
+    df.hvplot(y=y, kind=kind)
+
+
+@series_kinds
+def test_series_pandas(kind):
+    ser = pd.Series(np.random.rand(10), name="A")
+    ser.hvplot(kind=kind)
+
+
+@pytest.mark.skipif(skip_polar, reason="polars not installed")
+@pytest.mark.parametrize("cast", (pl.DataFrame, pl.LazyFrame))
+@frame_kinds
+@y_combinations
+def test_dataframe_polars(kind, y, cast):
+    df = cast(pd._testing.makeDataFrame())
+    assert isinstance(df, cast)
+    df.hvplot(y=y, kind=kind)
+
 
-    for t in types - ignore_types:
-        df.hvplot(y=y, kind=t)
+@pytest.mark.skipif(skip_polar, reason="polars not installed")
+@series_kinds
+def test_series_polars(kind):
+    ser = pl.Series(values=np.random.rand(10), name="A")
+    assert isinstance(ser, pl.Series)
+    ser.hvplot(kind=kind)

hvplot/tests/testpatch.py

@@ -100,3 +100,28 @@ def test_streamz_seriess_patched(self):
         from streamz.dataframe import Random
         random_df = Random()
         self.assertIsInstance(random_df.groupby('x').sum().y.hvplot, hvPlotTabular)
+
+
+class TestPatchPolars(TestCase):
+
+    def setUp(self):
+        try:
+            import polars as pl # noqa
+        except:
+            raise SkipTest('Polars not available')
+        import hvplot.polars   # noqa
+
+    def test_polars_series_patched(self):
+        import polars as pl
+        pseries = pl.Series([0, 1, 2])
+        self.assertIsInstance(pseries.hvplot, hvPlotTabular)
+
+    def test_polars_dataframe_patched(self):
+        import polars as pl
+        pdf = pl.DataFrame({'x': [1, 3, 5], 'y': [2, 4, 6]})
+        self.assertIsInstance(pdf.hvplot, hvPlotTabular)
+
+    def test_polars_lazyframe_patched(self):
+        import polars as pl
+        pldf = pl.LazyFrame({'x': [1, 3, 5], 'y': [2, 4, 6]})
+        self.assertIsInstance(pldf.hvplot, hvPlotTabular)

setup.py

@@ -60,6 +60,7 @@ def get_setup_version(reponame):
     'pooch',
     'scipy',
     'ipywidgets',
+    'polars',
 ]
 
 # Dependencies required to run the notebooks