Merge pull request #3817 from wf-r/selector_0_fix

FIX selector = 0 returns all traces in select_traces

Author: nicolaskruchten

Diff for: packages/python/plotly/plotly/basedatatypes.py

@@ -1139,7 +1139,7 @@ def select_traces(self, selector=None, row=None, col=None, secondary_y=None):
             Generator that iterates through all of the traces that satisfy
             all of the specified selection criteria
         """
-        if not selector:
+        if not selector and not isinstance(selector, int):
             selector = {}
 
         if row is not None or col is not None or secondary_y is not None:

Diff for: packages/python/plotly/plotly/tests/test_core/test_update_objects/test_update_traces.py

@@ -430,6 +430,10 @@ def select_traces_fixture():
 
 def test_select_traces_integer(select_traces_fixture):
     fig = select_traces_fixture
+    # check that selecting first trace does indeed only select the first
+    tr = list(fig.select_traces(selector=0))
+    assert len(tr) == 1
+    assert tr[0].y[1] == 0
     # check we can index last trace selected
     tr = list(fig.select_traces(selector=-1))[0]
     assert tr.y[1] == 20