Extend DataFrame parameter support to other libraries

param/parameters.py

@@ -2277,7 +2277,11 @@ def deserialize(cls, value):
 
 class DataFrame(ClassSelector):
     """
-    Parameter whose value is a pandas DataFrame.
+    Parameter whose value is a DataFrame of one of the enabled libraries.
+
+    The supported libraries can be controlled with the libraries argument.
+    Currently pandas is supported by default and both pandas and polars
+    can be enabled.
 
     The structure of the DataFrame can be constrained by the rows and
     columns arguments:
@@ -2294,31 +2298,54 @@ class DataFrame(ClassSelector):
     same columns and in the same order and no other columns.
     """
 
-    __slots__ = ['rows', 'columns', 'ordered']
+    __slots__ = ['rows', 'columns', 'ordered', 'libraries']
 
     _slot_defaults = _dict_update(
-        ClassSelector._slot_defaults, rows=None, columns=None, ordered=None
+        ClassSelector._slot_defaults, rows=None, columns=None, ordered=None, libraries=None
     )
 
+    _supported_libraries = ('pandas', 'polars')
+
     @typing.overload
     def __init__(
         self,
-        default=None, *, rows=None, columns=None, ordered=None, is_instance=True,
+        default=None, *, rows=None, columns=None, ordered=None, libraries=None, is_instance=True,
         allow_None=False, doc=None, label=None, precedence=None, instantiate=True,
         constant=False, readonly=False, pickle_default_value=True, per_instance=True,
         allow_refs=False, nested_refs=False
     ):
         ...
 
     @_deprecate_positional_args
-    def __init__(self, default=Undefined, *, rows=Undefined, columns=Undefined, ordered=Undefined, **params):
-        from pandas import DataFrame as pdDFrame
+    def __init__(self, default=Undefined, *, rows=Undefined, columns=Undefined, ordered=Undefined, libraries=Undefined, **params):
+        if libraries in (None, Undefined):
+            libraries = ('pandas',)
+        elif any(l not in self._supported_libraries for l in libraries):
+            raise ValueError(f'DataFrame parameter libraries must be one of {self._supported_libraries}')
         self.rows = rows
         self.columns = columns
         self.ordered = ordered
-        super().__init__(default=default, class_=pdDFrame, **params)
+        self.libraries = libraries
+        super().__init__(default=default, class_=None, **params)
         self._validate(self.default)
 
+    @property
+    def class_(self):
+        types = ()
+        if 'pandas' in self.libraries and 'pandas' in sys.modules:
+            import pandas as pd
+            types += (pd.DataFrame,)
+        if 'polars' in self.libraries and 'polars' in sys.modules:
+            import polars as pl
+            types += (pl.DataFrame, pl.LazyFrame)
+        if not types:
+            return type(None)
+        return types if len(types) > 1 else types[0]
+
+    @class_.setter
+    def class_(self, value):
+        pass # This is automatically determined from the libraries
+
     def _length_bounds_check(self, bounds, length, name):
         message = f'{name} length {length} does not match declared bounds of {bounds}'
         if not isinstance(bounds, tuple):
@@ -2374,6 +2401,10 @@ def _validate(self, val):
     def serialize(cls, value):
         if value is None:
             return None
+        if hasattr(value, 'collect'):
+            value = value.collect()  # Polars LazyFrame
+        if hasattr(value, 'to_dicts'):
+            return value.to_dicts()
         return value.to_dict('records')
 
     @classmethod