Simplify with or, msg lookup with dict.get() (#152)

compiler/block.py

@@ -33,11 +33,9 @@ class Package(object):
 
   def __init__(self, name, alias=None):
     self.name = name
-    if not alias:
       # Use Γ as a separator since it provides readability with a low
       # probability of name collisions.
-      alias = 'π_' + name.replace('/', 'Γ').replace('.', 'Γ')
-    self.alias = alias
+    self.alias = alias or 'π_' + name.replace('/', 'Γ').replace('.', 'Γ')
 
 
 class Loop(object):
@@ -423,8 +421,7 @@ class BlockVisitor(ast.NodeVisitor):
       self.vars[name] = Var(name, Var.TYPE_GLOBAL)
 
   def _register_local(self, name):
-    var = self.vars.get(name)
-    if not var:
+    if not self.vars.get(name):
       self.vars[name] = Var(name, Var.TYPE_LOCAL)