turned func into a property

story645 · story645 · commit e2d51818906c · 2020-05-03T00:00:27.000-04:00
diff --git a/lib/matplotlib/tests/test_ticker.py b/lib/matplotlib/tests/test_ticker.py
@@ -1066,6 +1066,11 @@ def test_other_builtins(self):
         with pytest.raises(UserWarning, match=r'max is not'):
             mticker.FuncFormatter(max)
 
+    def test_update(self):
+        formatter = mticker.FuncFormatter(lambda x, pos: f"{x}+{pos}")
+        assert "1+2" == formatter(1,2)
+        with pytest.raises(TypeError, match='3 arguments'):
+           formatter.func = lambda x, pos, error: "!"
 
 class TestStrMethodFormatter:
     test_data = [
diff --git a/lib/matplotlib/ticker.py b/lib/matplotlib/ticker.py
@@ -387,33 +387,42 @@ class FuncFormatter(Formatter):
     def __init__(self, func):
         self.func = func
 
+    def __call__(self, x, pos=None):
+        """
+        Return the value of the user defined function.
+
+        *x* and *pos* are passed through as-is.
+        """
+        if self._nargs == 1:
+            return self._func(x)
+        return self._func(x, pos)
+
+    @property
+    def func(self):
+        return self._func
+
+    @func.setter
+    def func(self, func):
+        self._func = func
         if not isinstance(func, types.BuiltinFunctionType):
-            self.nargs = len(inspect.signature(func).parameters)
+            self._nargs = len(inspect.signature(func).parameters)
         elif (isinstance(getattr(func, "__self__"), str) and
                 (getattr(func, "__name__", "") == "format")):
             #check if there's a format spec
-            self.nargs = len([(_, _, fs, _) for (_, _, fs, _)
+            self._nargs = len([(_, _, fs, _) for (_, _, fs, _)
                               in string.Formatter().parse(func.__self__)
                               if fs is not None])
         else:
             #finding argcount for other builtins is a mess
-            self.nargs = 2
+            self._nargs = 2
             cbook._warn_external(f"{func.__name__} is not supported "
                                   "and may not work as expected")
-        if self.nargs not in [1, 2]:
-            raise TypeError(f"{func.__name__} takes {self.nargs} arguments. "
+        if self._nargs not in [1, 2]:
+            raise TypeError(f"{func.__name__} takes {self._nargs} arguments. "
                              "FuncFormatter functions take at most 2: "
                              "x (required), pos (optional).")
+        
 
-    def __call__(self, x, pos=None):
-        """
-        Return the value of the user defined function.
-
-        *x* and *pos* are passed through as-is.
-        """
-        if self.nargs == 1:
-            return self.func(x)
-        return self.func(x, pos)
 
 
 class FormatStrFormatter(Formatter):
