matplotlib · tacaswell · Feb 9, 2023 · May 16, 2025 · May 16, 2025
diff --git a/doc/api/axes_api.rst b/doc/api/axes_api.rst
@@ -549,6 +549,8 @@ Interactive
    Axes.format_cursor_data
    Axes.format_xdata
    Axes.format_ydata
+   Axes.fmt_xdata
+   Axes.fmt_ydata
 
    Axes.mouseover
    Axes.in_axes

diff --git a/doc/api/toolkits/mplot3d/axes3d.rst b/doc/api/toolkits/mplot3d/axes3d.rst
@@ -246,6 +246,8 @@ Interactive
    format_zdata
    format_coord
 
+   fmt_zdata
+
 
 Projection and perspective
 --------------------------

diff --git a/galleries/users_explain/figure/interactive.rst b/galleries/users_explain/figure/interactive.rst
@@ -312,6 +312,29 @@ Preserve aspect ratio              hold **CONTROL** when panning/zooming with mo
 ================================== ===============================
 
 
+Position Format
+---------------
+
+The location of the cursor is shown in the UI and generated via the
+`~axes.Axes.format_coord` method which in turn calls the
+`~axes.Axes.format_xdata` and `~axes.Axes.format_ydata` methods.  The hard
+coded format in `~axes.Axes.format_coord` is ``f'x={formatted_x}
+y={formatted_y}'``.
+
+To easily customize how the x and y values are formatted, you can set the
+`.axes.Axes.fmt_xdata` and `.axes.Axes.fmt_ydata` attributes on the
+`~axes.Axes` instance.  The values are expected to be functions that
+take a float and return a string.  For example ::
+
+  fig, ax = plt.subplots()
+  ax.set_ylim(-5, 5)
+  ax.fmt_ydata = lambda v: f'{v:.3g}' if v > 0 else f'({-v:.3g})'
+
+will format negative y-values with parenthesis rather than a negative sign.  If
+these attributes are set to `None`, then the `.Formatter.format_data_short`
+method on the major formatter of the respective axes will be used instead.
+
+
 .. _other-shells:
 
 Other Python prompts

diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -7,6 +7,7 @@
 from operator import attrgetter
 import re
 import textwrap
+from typing import Callable
 import types
 
 import numpy as np
@@ -594,6 +595,23 @@ class _AxesBase(martist.Artist):
     - :doc:`Axis API </api/axis_api>`
     """
 
+    fmt_xdata: Callable[[float], str] | None
+    """
+    Callable to format the x-data in an interactive window.
+
+    The expected signature is ::
+
+        def fmt(val: float, /) -> str: ...
+    """
+
+    fmt_ydata: Callable[[float], str] | None
+    """
+    Callable to format the y-data in an interactive window.
+
+    The expected signature is ::
+
+        def fmt(val: float, /) -> str: ...
+    """
     def __str__(self):
         return "{0}({1[0]:g},{1[1]:g};{1[2]:g}x{1[3]:g})".format(
             type(self).__name__, self._position.bounds)

diff --git a/lib/mpl_toolkits/mplot3d/axes3d.py b/lib/mpl_toolkits/mplot3d/axes3d.py
@@ -14,6 +14,7 @@
 import itertools
 import math
 import textwrap
+from typing import Callable
 import warnings
 
 import numpy as np
@@ -57,6 +58,15 @@ class Axes3D(Axes):
     Axes._shared_axes["z"] = cbook.Grouper()
     Axes._shared_axes["view"] = cbook.Grouper()
 
+    fmt_zdata: Callable[[float], str] | None
+    """
+    Callable to format the z-data in an interactive window.
+
+    The expected signature is ::
+
+        def fmt(val: float, /) -> str: ...
+    """
+
     def __init__(
         self, fig, rect=None, *args,
         elev=30, azim=-60, roll=0, shareview=None, sharez=None,