Add DecimalConverter in units.py

sasoripathos · sasoripathos · commit 7359ece1a380 · 2019-04-19T16:06:39.000-04:00
In axis.py, instead of first checking whether input is number like, direct handle them as a united quantity.
Since Decimal is a kind of Number, so DecimalConvert doesn't need to provide extra AxisInfo or default unit.
diff --git a/lib/matplotlib/axis.py b/lib/matplotlib/axis.py
@@ -6,8 +6,6 @@
 import logging
 
 import numpy as np
-from numpy import ma
-from decimal import Decimal
 
 from matplotlib import rcParams
 import matplotlib.artist as martist
@@ -1545,27 +1543,6 @@ def have_units(self):
         return self.converter is not None or self.units is not None
 
     def convert_units(self, x):
-        # If x is already a number
-        if munits.ConversionInterface.is_numlike(x):
-            if np.iterable(x):
-                is_decimal = False
-                # use iterator to avoid key error
-                for thisx in x:
-                    is_decimal = isinstance(thisx, Decimal)
-                if is_decimal:
-                    converter = np.asarray
-                    if isinstance(x, ma.MaskedArray):
-                        converter = ma.asarray
-                    return converter(x, dtype=np.float)
-                else:
-                    return x
-            # need to convert when x is a Decimal
-            elif isinstance(x, Decimal):
-                return np.float(x)
-            # Otherwise, doesn't need converting
-            else:
-                return x
-
         if self.converter is None:
             self.converter = munits.registry.get_converter(x)
 
@@ -1574,8 +1551,16 @@ def convert_units(self, x):
         try:
             ret = self.converter.convert(x, self.units, self)
         except Exception as e:
-            raise munits.ConversionError('Failed to convert value(s) to axis '
-                                         f'units: {x!r}') from e
+            # If x is already number like, converters other than
+            # DecimalConverter may raise error, so check here to walk around.
+            if munits.ConversionInterface.is_numlike(x):
+                return x
+            # Try convert again
+            try:
+                ret = self.converter.convert(x, self.units, self)
+            except Exception as e2:
+                raise munits.ConversionError('Failed to convert value(s) to '
+                                         f'axis units: {x!r}') from e2
         return ret
 
     def set_units(self, u):
diff --git a/lib/matplotlib/units.py b/lib/matplotlib/units.py
@@ -45,6 +45,8 @@ def default_units(x, axis):
 from numbers import Number
 
 import numpy as np
+from numpy import ma
+from decimal import Decimal
 
 from matplotlib import cbook
 
@@ -133,6 +135,43 @@ def is_numlike(x):
             return isinstance(x, Number)
 
 
+class DecimalConverter(ConversionInterface):
+    """
+    Converter for decimal.Decimal data to float.
+    """
+    @staticmethod
+    def convert(value, unit, axis):
+        """
+        Convert Decimals to floats.
+
+        The *unit* and *axis* arguments are not used.
+
+        Parameters
+        ----------
+        value : decimal.Decimal or iterable
+            Decimal or list of Decimal need to be converted
+        """
+        # If value is a Decimal
+        if isinstance(value, Decimal):
+            return np.float(value)
+        # else x is a list of Decimal
+        else:
+            converter = np.asarray
+            if isinstance(value, ma.MaskedArray):
+                converter = ma.asarray
+            return converter(value, dtype=np.float)
+
+    @staticmethod
+    def axisinfo(unit, axis):
+        # Since Decimal is a kind of Number, don't need specific axisinfo.
+        return AxisInfo()
+
+    @staticmethod
+    def default_units(x, axis):
+        # Return None since Decimal is a kind of Number.
+        return None
+
+
 class Registry(dict):
     """Register types with conversion interface."""
 
@@ -164,3 +203,4 @@ def get_converter(self, x):
 
 
 registry = Registry()
+registry[Decimal] = DecimalConverter()
