Enable syncing dataframe parameters

panel/io/cache.py

@@ -112,6 +112,10 @@ def _pandas_hash(obj):
     if len(obj) >= _PANDAS_ROWS_LARGE:
         obj = obj.sample(n=_PANDAS_SAMPLE_SIZE, random_state=0)
     try:
+        if isinstance(obj, pd.DataFrame):
+            return ((b"%s" % pd.util.hash_pandas_object(obj).sum())
+                + (b"%s" % pd.util.hash_pandas_object(obj.columns).sum())
+            )
         return b"%s" % pd.util.hash_pandas_object(obj).sum()
     except TypeError:
         # Use pickle if pandas cannot hash the object for example if
@@ -463,3 +467,10 @@ def server_clear(session_context):
         pass
 
     return wrapped_func
+
+def is_equal(value, other)->bool:
+    """Returns True if value and other are equal
+
+    Supports complex values like DataFrames
+    """
+    return value is other or _generate_hash(value)==_generate_hash(other)

panel/io/location.py

@@ -15,6 +15,7 @@
 from ..models.location import Location as _BkLocation
 from ..reactive import Syncable
 from ..util import edit_readonly, parse_query
+from .cache import is_equal
 from .document import create_doc_if_none_exists
 from .state import state
 
@@ -24,7 +25,6 @@
     from bokeh.server.contexts import BokehSessionContext
     from pyviz_comms import Comm
 
-
 class Location(Syncable):
     """
     The Location component can be made available in a server context
@@ -164,9 +164,10 @@ def _update_synced(self, event: param.parameterized.Event = None) -> None:
                 except Exception:
                     pass
                 try:
-                    equal = v == getattr(p, pname)
+                    equal = is_equal(v, getattr(p, pname))
                 except Exception:
                     equal = False
+
                 if not equal:
                     mapped[pname] = v
             try:

panel/tests/io/test_cache.py

@@ -17,7 +17,9 @@
     diskcache = None
 diskcache_available = pytest.mark.skipif(diskcache is None, reason="requires diskcache")
 
-from panel.io.cache import _find_hash_func, cache
+from panel.io.cache import (
+    _find_hash_func, _generate_hash, cache, is_equal,
+)
 from panel.io.state import set_curdoc, state
 from panel.tests.util import serve_and_wait
 
@@ -339,3 +341,20 @@ def expensive_calculation(self, value):
     assert model.expensive_calculation(2) == 4
 
     assert model.executions == 2
+
+DF1 = pd.DataFrame({"x": [1]})
+DF2 = pd.DataFrame({"y": [1]})
+
+def test_hash_on_simple_dataframes():
+    assert _generate_hash(DF1)!=_generate_hash(DF2)
+
+@pytest.mark.parametrize(["value", "other", "expected"], [
+    (None, None, True),
+    (True, False, False), (False, True, False), (False, False, True), (True, True, True),
+    (None, 1, False), (1, None, False), (1, 1, True), (1,2,False),
+    (None, "a", False), ("a", None, False), ("a", "a", True), ("a","b",False),
+    (1,"1", False),
+    (None, DF1, False), (DF1, None, False), (DF1, DF1, True), (DF1, DF1.copy(), True), (DF1,DF2,False),
+])
+def test_is_equal(value, other, expected):
+    assert is_equal(value, other)==expected

panel/tests/io/test_location.py

@@ -1,3 +1,4 @@
+import pandas as pd
 import param
 import pytest
 
@@ -26,6 +27,8 @@ class SyncParameterized(param.Parameterized):
 
     string = param.String(default=None)
 
+    dataframe = param.DataFrame(default=None)
+
 
 def test_location_update_query(location):
     location.update_query(a=1)
@@ -164,3 +167,24 @@ def app():
 
 def test_iframe_srcdoc_location():
     Location(pathname="srcdoc")
+
+@pytest.fixture
+def dataframe():
+    return pd.DataFrame({"x": [1]})
+
+def test_location_sync_from_dataframe(location, dataframe):
+    p = SyncParameterized(dataframe=dataframe)
+    location.sync(p)
+    assert location.search == "?dataframe=%5B%7B%22x%22%3A+1%7D%5D"
+
+def test_location_sync_to_dataframe(location, dataframe):
+    p = SyncParameterized()
+    location.search = "?dataframe=%5B%7B%22x%22%3A+1%7D%5D"
+    location.sync(p)
+    pd.testing.assert_frame_equal(p.dataframe, dataframe)
+
+def test_location_sync_to_dataframe_with_initial_value(location, dataframe):
+    p = SyncParameterized(dataframe=pd.DataFrame({"y": [2]}))
+    location.search = "?dataframe=%5B%7B%22x%22%3A+1%7D%5D"
+    location.sync(p)
+    pd.testing.assert_frame_equal(p.dataframe, dataframe)