symbol accessor optimization for string formatting

2 files changed, 4 insertions, 1 deletions

diff --git a/pint/quantity.py b/pint/quantity.py
index 9f072b8..4e18f83 100644
--- a/pint/quantity.py
+++ b/pint/quantity.py
@@ -126,7 +126,7 @@ class _Quantity(object):
         spec = spec or self.default_format
 
         if '~' in spec:
-            units = UnitsContainer(dict((self._REGISTRY.get_symbol(key), value)
+            units = UnitsContainer(dict((self._REGISTRY._get_symbol(key), value)
                                    for key, value in self.units.items()))
             spec = spec.replace('~', '')
         else:
diff --git a/pint/unit.py b/pint/unit.py
index 0864c4d..95af3be 100644
--- a/pint/unit.py
+++ b/pint/unit.py
@@ -880,6 +880,9 @@ class UnitRegistry(object):
 
         return self._prefixes[prefix].symbol + self._units[unit_name].symbol
 
+    def _get_symbol(self, name):
+        return self._units[name].symbol
+
     def get_dimensionality(self, input_units):
         """Convert unit or dict of units or dimensions to a dict of base dimensions