ENH: option to change the number in _dir_additions_for_owner

pandas/core/config_init.py

@@ -236,6 +236,16 @@ def use_numba_cb(key):
     (default: True)
 """
 
+pc_max_dir_items = """\
+: int
+    The number of items that will be added to `dir(...)`. 'None' value means
+    unlimited. Because dir is cached, changing this option will not immediately
+    affect already existing dataframes until a column is deleted or added.
+
+    This is for instance used to suggest columns from a dataframe to tab
+    completion.
+"""
+
 pc_width_doc = """
 : int
     Width of the display in characters. In case python/IPython is running in
@@ -449,6 +459,9 @@ def _deprecate_negative_int_max_colwidth(key):
     cf.register_option(
         "html.use_mathjax", True, pc_html_use_mathjax_doc, validator=is_bool
     )
+    cf.register_option(
+        "max_dir_items", 100, pc_max_dir_items, validator=is_nonnegative_int
+    )
 
 tc_sim_interactive_doc = """
 : boolean

pandas/core/indexes/base.py

@@ -846,7 +846,7 @@ def _dir_additions_for_owner(self) -> set[str_t]:
         """
         return {
             c
-            for c in self.unique(level=0)[:100]
+            for c in self.unique(level=0)[: get_option("display.max_dir_items")]
             if isinstance(c, str) and c.isidentifier()
         }