Refactored DecimalNumber to better use string formatting syntax

mobject/numbers.py

@@ -1,6 +1,7 @@
 from __future__ import absolute_import
 
 from constants import *
+import operator as op
 
 from mobject.svg.tex_mobject import SingleStringTexMobject
 from mobject.types.vectorized_mobject import VMobject
@@ -9,33 +10,28 @@ from mobject.types.vectorized_mobject import VMobject
 class DecimalNumber(VMobject):
     CONFIG = {
         "num_decimal_places": 2,
+        "include_sign": False,
+        "group_with_commas": True,
         "digit_to_digit_buff": 0.05,
         "show_ellipsis": False,
         "unit": None,  # Aligned to bottom unless it starts with "^"
         "include_background_rectangle": False,
-        "include_sign": False,
     }
 
     def __init__(self, number, **kwargs):
         VMobject.__init__(self, **kwargs)
         # TODO, make this more ediable with a getter and setter
         self.number = number
-        ndp = self.num_decimal_places
 
-        # Build number string
         if isinstance(number, complex):
-            num_string = '%.*f%s%.*fi' % (
-                ndp, number.real,
-                "-" if number.imag < 0 else "+",
-                ndp, abs(number.imag)
-            )
+            formatter = self.get_complex_formatter()
         else:
-            num_string = '%.*f' % (ndp, number)
-            if self.include_sign and number >= 0:
-                num_string = "+" + num_string
-            negative_zero_string = "-%.*f" % (ndp, 0.)
-            if num_string == negative_zero_string:
-                num_string = num_string[1:]
+            formatter = self.get_formatter()
+        num_string = formatter.format(number)
+
+        if num_string.startswith("-") and number == 0:
+            num_string = num_string[1:]
+
         self.add(*[
             SingleStringTexMobject(char, **kwargs)
             for char in num_string
@@ -66,12 +62,39 @@ class DecimalNumber(VMobject):
         for i, c in enumerate(num_string):
             if c == "-" and len(num_string) > i + 1:
                 self[i].align_to(self[i + 1], alignment_vect=UP)
+            elif c == ",":
+                self[i].shift(self[i].get_height() * DOWN / 2)
         if self.unit and self.unit.startswith("^"):
             self.unit_sign.align_to(self, UP)
         #
         if self.include_background_rectangle:
             self.add_background_rectangle()
 
+    def get_formatter(self, **kwargs):
+        """
+        Configuration is based first off instance attributes,
+        but overwritten by any kew word argument.  Relevant
+        key words:
+        - include_sign
+        - group_with_commas
+        - num_decimal_places
+        - field_name (e.g. 0 or 0.real)
+        """
+        config = dict(self.__dict__)
+        config.update(kwargs)
+        return reduce(op.add, [
+            "{",
+            config.get("field_name", ""),
+            ":",
+            "+" if config["include_sign"] else "",
+            "," if config["group_with_commas"] else "",
+            ".", str(config["num_decimal_places"]), "f",
+            "}",
+        ])
+
+    def get_complex_formatter(self, **kwargs):
+        pass
+
 
 class Integer(DecimalNumber):
     CONFIG = {