Permit any Mapping as source of DataFrame

Author: mrkn

pandas/core/frame.py

@@ -739,7 +739,7 @@ def __init__(
             raise ValueError("columns cannot be a set")
 
         if copy is None:
-            if isinstance(data, dict):
+            if isinstance(data, Mapping):
                 # retain pre-GH#38939 default behavior
                 copy = True
             elif not isinstance(data, (Index, DataFrame, Series)):
@@ -758,7 +758,7 @@ def __init__(
                 data, axes={"index": index, "columns": columns}, dtype=dtype, copy=copy
             )
 
-        elif isinstance(data, dict):
+        elif isinstance(data, Mapping):
             # GH#38939 de facto copy defaults to False only in non-dict cases
             mgr = dict_to_mgr(data, index, columns, dtype=dtype, copy=copy)
         elif isinstance(data, ma.MaskedArray):

pandas/core/internals/construction.py

@@ -347,7 +347,7 @@ def _check_values_indices_shape_match(
 
 
 def dict_to_mgr(
-    data: dict,
+    data: Mapping,
     index,
     columns,
     *,