matplotlib · timhoffm · Mar 28, 2026
diff --git a/doc/api/next_api_changes/deprecations/31416-TH.rst b/doc/api/next_api_changes/deprecations/31416-TH.rst
@@ -0,0 +1,8 @@
+Formatter attributes
+~~~~~~~~~~~~~~~~~~~~
+
+These following attributes are considered internal and users should not have a need to access them:
+
+- `.ScalarFormatter`: ``orderOfMagnitude`` and ``format``
+- `.ConciseDateFormatter`: ``offset_format``
+- `.Formatter`: ``locs``
diff --git a/lib/matplotlib/dates.py b/lib/matplotlib/dates.py
@@ -665,6 +665,10 @@ class ConciseDateFormatter(ticker.Formatter):
 
     """
 
+    offset_string = _api.deprecate_privatize_attribute(
+        "3.11", alternative="get_offset()"
+    )
+
     def __init__(self, locator, tz=None, formats=None, offset_formats=None,
                  zero_formats=None, show_offset=True, *, usetex=None):
         """
@@ -719,7 +723,7 @@ def __init__(self, locator, tz=None, formats=None, offset_formats=None,
                                    '%Y-%b-%d',
                                    '%Y-%b-%d',
                                    '%Y-%b-%d %H:%M']
-        self.offset_string = ''
+        self._offset_string = ''
         self.show_offset = show_offset
         self._usetex = mpl._val_or_rc(usetex, 'text.usetex')
 

diff --git a/lib/matplotlib/testing/jpl_units/UnitDblFormatter.py b/lib/matplotlib/testing/jpl_units/UnitDblFormatter.py
@@ -14,7 +14,7 @@ class UnitDblFormatter(ticker.ScalarFormatter):
 
     def __call__(self, x, pos=None):
         # docstring inherited
-        if len(self.locs) == 0:
+        if len(self._locs) == 0:
             return ''
         else:
             return f'{x:.12}'

diff --git a/lib/matplotlib/tests/test_ticker.py b/lib/matplotlib/tests/test_ticker.py
@@ -920,7 +920,7 @@ def test_scilimits(self, sci_type, scilimits, lim, orderOfMag, fewticks):
             ax.yaxis.set_major_locator(mticker.MaxNLocator(4))
 
         tmp_form.set_locs(ax.yaxis.get_majorticklocs())
-        assert orderOfMag == tmp_form.orderOfMagnitude
+        assert orderOfMag == tmp_form._orderOfMagnitude
 
     @pytest.mark.parametrize('value, expected', format_data)
     def test_format_data(self, value, expected):

diff --git a/lib/matplotlib/ticker.py b/lib/matplotlib/ticker.py
@@ -202,7 +202,9 @@ class Formatter(TickHelper):
     """
     # some classes want to see all the locs to help format
     # individual ones
-    locs = []
+    _locs = []
+
+    locs = _api.deprecate_privatize_attribute("3.11")
 
     def __call__(self, x, pos=None):
         """
@@ -250,7 +252,7 @@ def set_locs(self, locs):
         This method is called before computing the tick labels because some
         formatters need to know all tick locations to do so.
         """
-        self.locs = locs
+        self._locs = locs
 
     @staticmethod
     def fix_minus(s):
@@ -458,15 +460,18 @@ class ScalarFormatter(Formatter):
 
     """
 
+    orderOfMagnitude = _api.deprecate_privatize_attribute("3.11")
+    format = _api.deprecate_privatize_attribute("3.11")
+
     def __init__(self, useOffset=None, useMathText=None, useLocale=None, *,
                  usetex=None):
         useOffset = mpl._val_or_rc(useOffset, 'axes.formatter.useoffset')
         self._offset_threshold = mpl.rcParams['axes.formatter.offset_threshold']
         self.set_useOffset(useOffset)
         self.set_usetex(usetex)
         self.set_useMathText(useMathText)
-        self.orderOfMagnitude = 0
-        self.format = ''
+        self._orderOfMagnitude = 0
+        self._format = ''
         self._scientific = True
         self._powerlimits = mpl.rcParams['axes.formatter.limits']
         self.set_useLocale(useLocale)
@@ -1446,7 +1451,7 @@ def __call__(self, x, pos=None):
             xp = (x - self.offset) / (10. ** self.orderOfMagnitude)
             if abs(xp) < 1e-8:
                 xp = 0
-            return self._format_maybe_minus_and_locale(self.format, xp)
+            return self._format_maybe_minus_and_locale(self._format, xp)
 
     def set_locs(self, locs):
         # docstring inherited

diff --git a/lib/matplotlib/ticker.pyi b/lib/matplotlib/ticker.pyi
@@ -24,6 +24,7 @@ class TickHelper:
 
 class Formatter(TickHelper):
     locs: list[float]
+    _locs: list[float]
     def __call__(self, x: float, pos: int | None = ...) -> str: ...
     def format_ticks(self, values: list[float]) -> list[str]: ...
     def format_data(self, value: float) -> str: ...
@@ -58,7 +59,9 @@ class StrMethodFormatter(Formatter):
 
 class ScalarFormatter(Formatter):
     orderOfMagnitude: int
+    _orderOfMagnitude: int
     format: str
+    _format: str
     def __init__(
         self,
         useOffset: bool | float | None = ...,