fix: define to_pandas/to_pyarrow on DataType/Schema classes directly

ibis/backends/pandas/client.py

@@ -308,10 +308,6 @@ def try_json(x):
     return pd.Series(list(map(try_json, col)), dtype="object")
 
 
-dt.DataType.to_pandas = ibis_dtype_to_pandas  # type: ignore
-sch.Schema.to_pandas = ibis_schema_to_pandas  # type: ignore
-
-
 class DataFrameProxy(Immutable, util.ToFrame):
     __slots__ = ('_df', '_hash')
 

ibis/backends/pyarrow/datatypes.py

@@ -138,7 +138,3 @@ def ibis_to_pyarrow_struct(schema: sch.Schema) -> pa.StructType:
 
 def ibis_to_pyarrow_schema(schema: sch.Schema) -> pa.Schema:
     return pa.schema(_schema_to_pyarrow_schema_fields(schema))
-
-
-dt.DataType.to_pyarrow = to_pyarrow_type  # type: ignore
-sch.Schema.to_pyarrow = ibis_to_pyarrow_schema  # type: ignore

ibis/expr/datatypes/core.py

@@ -78,6 +78,18 @@ def castable(self, other, **kwargs):
 
         return castable(self, other, **kwargs)
 
+    def to_pandas(self):
+        """Return the equivalent pandas datatype."""
+        from ibis.backends.pandas.client import ibis_dtype_to_pandas
+
+        return ibis_dtype_to_pandas(self)
+
+    def to_pyarrow(self):
+        """Return the equivalent pyarrow datatype."""
+        from ibis.backends.pyarrow.datatypes import to_pyarrow_type
+
+        return to_pyarrow_type(self)
+
     def is_array(self) -> bool:
         return isinstance(self, Array)
 

ibis/expr/schema.py

@@ -197,6 +197,18 @@ def from_dict(cls, dictionary: Mapping[str, str | dt.DataType]) -> Schema:
         names, types = zip(*dictionary.items()) if dictionary else ([], [])
         return cls(names, types)
 
+    def to_pandas(self):
+        """Return the equivalent pandas datatypes."""
+        from ibis.backends.pandas.client import ibis_schema_to_pandas
+
+        return ibis_schema_to_pandas(self)
+
+    def to_pyarrow(self):
+        """Return the equivalent pyarrow schema."""
+        from ibis.backends.pyarrow.datatypes import ibis_to_pyarrow_schema
+
+        return ibis_to_pyarrow_schema(self)
+
     def __gt__(self, other: Schema) -> bool:
         """Return whether `self` is a strict superset of `other`."""
         return set(self.items()) > set(other.items())