Deprecate passing a string as *num* argument

afvincent · afvincent · commit ac42b94e990e · 2017-08-25T09:39:46.000-07:00
diff --git a/doc/api/api_changes/2017-08-24-deprecation-in-engformatter.rst b/doc/api/api_changes/2017-08-24-deprecation-in-engformatter.rst
@@ -0,0 +1,5 @@
+Deprecation in EngFormatter
+```````````````````````````
+
+Passing a string as *num* argument when calling an instance of
+`matplotlib.ticker.EngFormatter` is deprecated and will be removed in 2.3.
diff --git a/lib/matplotlib/ticker.py b/lib/matplotlib/ticker.py
@@ -1262,6 +1262,12 @@ def format_eng(self, num):
         `num` may be a numeric value or a string that can be converted
         to a numeric value with ``float(num)``.
         """
+        if isinstance(num, six.string_types):
+            warnings.warn(
+                "Passing a string as *num* argument is deprecated since"
+                "Matplotlib 2.1, and is expected to be removed in 2.3.",
+                mplDeprecation)
+
         dnum = float(num)
         sign = 1
         fmt = "g" if self.places is None else ".{:d}f".format(self.places)
