add sorted queue type, make it the default

boltons/queueutils.py

@@ -12,9 +12,9 @@ except ImportError:
 
 try:
     from listutils import BList
-    list_type = BList  # see BarrelList docstring for notes
+    # see BarrelList docstring for notes
 except ImportError:
-    list_type = list
+    BList = list
 
 
 __all__ = ['PriorityQueue', 'HeapPriorityQueue', 'SortedPriorityQueue']
@@ -27,10 +27,10 @@ __all__ = ['PriorityQueue', 'HeapPriorityQueue', 'SortedPriorityQueue']
 class BasePriorityQueue(object):
     # negating priority means larger numbers = higher priority
     _default_priority_key = staticmethod(lambda p: -int(p or 0))
-    _list_type = list
+    _backend_type = list
 
     def __init__(self, **kw):
-        self._pq = self._list_type()
+        self._pq = self._backend_type()
         self._entry_map = {}
         self._counter = itertools.count()
         self._get_priority = kw.pop('priority_key', self._default_priority_key)
@@ -102,10 +102,18 @@ class HeapPriorityQueue(BasePriorityQueue):
 
 
 class SortedPriorityQueue(BasePriorityQueue):
-    pass
+    _backend_type = BList
+
+    @staticmethod
+    def _pop_entry(backend):
+        return backend.pop(0)
+
+    @staticmethod
+    def _push_entry(backend, entry):
+        insort(backend, entry)
 
 
-PriorityQueue = HeapPriorityQueue
+PriorityQueue = SortedPriorityQueue
 
 # tests
 
@@ -119,6 +127,13 @@ def main():
     assert len(pq) == 1
     assert func == pq.pop()
     assert len(pq) == 0
+    try:
+        pq.pop()
+    except IndexError:
+        pass
+    else:
+        assert False, 'priority queue should be empty'
+    import pdb;pdb.set_trace()
 
 if __name__ == '__main__':
     try: