ENH: Validation to only allow positive integers for options (pandas-dev#27382)

Author: Adam-Klaum

doc/source/whatsnew/v1.0.0.rst

@@ -195,6 +195,12 @@ ExtensionArray
 -
 -
 
+
+Other
+^^^^^
+- Trying to set the ``display.precision``, ``display.max_rows`` or ``display.max_columns`` using :meth:`set_option` to anything but a ``None`` or a positive int will raise a ``ValueError`` (:issue:`23348`)
+
+
 .. _whatsnew_1000.contributors:
 
 Contributors

pandas/_config/config.py

@@ -787,6 +787,7 @@ def is_instance_factory(_type):
                 ValueError if x is not an instance of `_type`
 
     """
+
     if isinstance(_type, (tuple, list)):
         _type = tuple(_type)
         type_repr = "|".join(map(str, _type))
@@ -820,6 +821,32 @@ def inner(x):
     return inner
 
 
+def is_nonnegative_int(value):
+    """
+    Verify that value is None or a positive int.
+
+    Parameters
+    ----------
+    value : None or int
+            The `value` to be checked.
+
+    Raises
+    ------
+    ValueError
+        When the value is not None or is a negative integer
+    """
+
+    if value is None:
+        return
+
+    elif isinstance(value, int):
+        if value >= 0:
+            return
+
+    msg = "Value must be a nonnegative integer or None"
+    raise ValueError(msg)
+
+
 # common type validators, for convenience
 # usage: register_option(... , validator = is_int)
 is_int = is_type_factory(int)

pandas/core/config_init.py

@@ -17,6 +17,7 @@
     is_callable,
     is_instance_factory,
     is_int,
+    is_nonnegative_int,
     is_one_of_factory,
     is_text,
 )
@@ -319,7 +320,7 @@ def is_terminal():
 
 
 with cf.config_prefix("display"):
-    cf.register_option("precision", 6, pc_precision_doc, validator=is_int)
+    cf.register_option("precision", 6, pc_precision_doc, validator=is_nonnegative_int)
     cf.register_option(
         "float_format",
         None,
@@ -333,12 +334,7 @@ def is_terminal():
         pc_max_info_rows_doc,
         validator=is_instance_factory((int, type(None))),
     )
-    cf.register_option(
-        "max_rows",
-        60,
-        pc_max_rows_doc,
-        validator=is_instance_factory([type(None), int]),
-    )
+    cf.register_option("max_rows", 60, pc_max_rows_doc, validator=is_nonnegative_int)
     cf.register_option(
         "min_rows",
         10,
@@ -352,10 +348,7 @@ def is_terminal():
     else:
         max_cols = 20  # cannot determine optimal number of columns
     cf.register_option(
-        "max_columns",
-        max_cols,
-        pc_max_cols_doc,
-        validator=is_instance_factory([type(None), int]),
+        "max_columns", max_cols, pc_max_cols_doc, validator=is_nonnegative_int
     )
     cf.register_option(
         "large_repr",

pandas/tests/config/test_config.py

@@ -208,20 +208,33 @@ def test_set_option_multiple(self):
 
     def test_validation(self):
         self.cf.register_option("a", 1, "doc", validator=self.cf.is_int)
+        self.cf.register_option("d", 1, "doc", validator=self.cf.is_nonnegative_int)
         self.cf.register_option("b.c", "hullo", "doc2", validator=self.cf.is_text)
+
         msg = "Value must have type '<class 'int'>'"
         with pytest.raises(ValueError, match=msg):
             self.cf.register_option("a.b.c.d2", "NO", "doc", validator=self.cf.is_int)
 
         self.cf.set_option("a", 2)  # int is_int
         self.cf.set_option("b.c", "wurld")  # str is_str
+        self.cf.set_option("d", 2)
 
         # None not is_int
         with pytest.raises(ValueError, match=msg):
             self.cf.set_option("a", None)
         with pytest.raises(ValueError, match=msg):
             self.cf.set_option("a", "ab")
 
+        msg = "Value must be a nonnegative integer or None"
+        with pytest.raises(ValueError, match=msg):
+            self.cf.register_option(
+                "a.b.c.d3", "NO", "doc", validator=self.cf.is_nonnegative_int
+            )
+        with pytest.raises(ValueError, match=msg):
+            self.cf.register_option(
+                "a.b.c.d3", -2, "doc", validator=self.cf.is_nonnegative_int
+            )
+
         msg = r"Value must be an instance of <class 'str'>\|<class 'bytes'>"
         with pytest.raises(ValueError, match=msg):
             self.cf.set_option("b.c", 1)