enable assignment operators and add substraction support for numbers

jedi/evaluate/__init__.py

@@ -126,8 +126,8 @@ class Evaluator(object):
 
         ass_details = stmt.assignment_details
         if ass_details and ass_details[0][1] != '=' and not isinstance(stmt,
-er.InstanceElement) and False:  # TODO don't check for this.
-            print('LEFT', ass_details, stmt, stmt.parent)
+er.InstanceElement):  # TODO don't check for this.
+            #print('LEFT', ass_details, stmt, stmt.parent)
             expr_list, operator = ass_details[0]
             name = str(expr_list[0].name)
             start_pos = stmt.start_pos[0] - 1, stmt.start_pos[1] + 30000

jedi/evaluate/precedence.py

@@ -202,4 +202,7 @@ def _element_calculate(left, operator, right):
     elif operator == '+':
         if is_number(left) and is_number(right) or is_string(left) and is_string(right):
             return [create(left.obj + right.obj)]
+    elif operator == '-':
+        if is_number(left) and is_number(right):
+            return [create(left.obj - right.obj)]
     return [left, right]

test/completion/operators.py

@@ -64,3 +64,10 @@ i += 1
 i += 1
 #? float()
 x[i]
+
+i = 1
+i += 1
+i -= 3
+i += 1
+#? int()
+x[i]