diff --git a/notebooks/shared/jinja2/lexer.py b/notebooks/shared/jinja2/lexer.py
index 6fd135dd..e4368b39 100644
--- a/notebooks/shared/jinja2/lexer.py
+++ b/notebooks/shared/jinja2/lexer.py
@@ -136,7 +136,7 @@
     ';':            TOKEN_SEMICOLON
 }
 
-reverse_operators = dict([(v, k) for k, v in iteritems(operators)])
+reverse_operators = {v: k for k, v in iteritems(operators)}
 assert len(operators) == len(reverse_operators), 'operators dropped'
 operator_re = re.compile('(%s)' % '|'.join(re.escape(x) for x in
                          sorted(operators, key=lambda x: -len(x))))