add pd.options.mode.data_manager to switch

pandas/core/config_init.py

@@ -482,6 +482,12 @@ def use_inf_as_na_cb(key):
     cf.register_option(
         "use_inf_as_null", False, use_inf_as_null_doc, cb=use_inf_as_na_cb
     )
+    cf.register_option(
+        "data_manager",
+        "block",
+        "internal manager type",
+        validator=is_one_of_factory(["block", "array"]),
+    )
 
 cf.deprecate_option(
     "mode.use_inf_as_null", msg=use_inf_as_null_doc, rkey="mode.use_inf_as_na"

pandas/core/frame.py

@@ -448,7 +448,7 @@ def __init__(
         copy: bool = False,
         # TODO setting default to "array" for testing purposes (the actual default
         # needs to stay "block" initially of course for backwards compatibility)
-        manager: str = "array",
+        manager: Optional[str] = None,
     ):
         if data is None:
             data = {}
@@ -567,11 +567,16 @@ def __init__(
                     values, index, columns, dtype=values.dtype, copy=False
                 )
 
+        if manager is None:
+            manager = get_option("mode.data_manager")
+
         if manager == "array" and not isinstance(mgr, ArrayManager):
             # TODO proper initialization
             df = DataFrame(mgr, manager="block")
             arrays = [arr.copy() for arr in df._iter_column_arrays()]
             mgr = ArrayManager(arrays, [mgr.axes[1], mgr.axes[0]])
+        # TODO check for case of manager="block" but mgr is ArrayManager
+
         NDFrame.__init__(self, mgr)
 
     # ----------------------------------------------------------------------