Bug #639906: Adding __str__ and __unicode__ methods to GncNumeric

Patch by Christoph Holtermann:

1) I decided to let the methods return "Division by Zero" for denom()==0.
2) As proposed in
http://stackoverflow.com/questions/1307014/python-str-versus-unicode i created
both __str__ and __unicode__.
3) I use format to fix the decimal places to 2. It would be nice if the number
would be configurable.

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@20128 57a11ea4-9604-0410-9ed3-97b8803252fd

src/optional/python-bindings/gnucash_core.py

@@ -236,7 +236,7 @@ class GncNumeric(GnuCashCoreClass):
     and GNC_HOW_DENOM_FIXED are available for arithmetic
     functions like GncNumeric.add
 
-    Look at gnc-numeric.h to see how ot use these
+    Look at gnc-numeric.h to see how to use these
     """
 
     def __init__(self, num=0, denom=1, **kargs):
@@ -251,6 +251,19 @@ class GncNumeric(GnuCashCoreClass):
         #    self.set_denom(denom) # currently undefined
         #    self.set_num(num)     # currently undefined
 
+    def __unicode__(self):
+        """Returns a human readable numeric value string as UTF8."""
+        if self.denom() == 0:
+            return "Division by zero"
+        else:
+            value_float = self.to_double() 
+            value_str   = u"{0:.{1}f}".format(value_float,2) ## The second argument is the precision. It would be nice to be able to make it configurable.
+            return value_str
+
+    def __str__(self):
+        """returns a human readable numeric value string as bytes."""
+        return unicode(self).encode('utf-8')
+
 class GncPrice(GnuCashCoreClass):
     '''
     Each priceEach price in the database represents an "instantaneous"