diff --git a/tf2onnx/tf_utils.py b/tf2onnx/tf_utils.py
index 362e3551b..de51b66d3 100644
--- a/tf2onnx/tf_utils.py
+++ b/tf2onnx/tf_utils.py
@@ -13,7 +13,6 @@
 from distutils.version import LooseVersion
 
 import numpy as np
-import six
 import tensorflow as tf
 
 from tensorflow.core.framework import types_pb2, tensor_pb2
@@ -70,7 +69,7 @@ def get_tf_tensor_data(tensor):
     """Get data from tensor."""
     make_sure(isinstance(tensor, tensor_pb2.TensorProto), "Require TensorProto")
     np_data = tensor_util.MakeNdarray(tensor)
-    make_sure(isinstance(np_data, np.ndarray), "{} isn't ndarray".format(np_data))
+    make_sure(isinstance(np_data, np.ndarray), "%r isn't ndarray", np_data)
     return np_data
 
 
@@ -83,7 +82,7 @@ def get_tf_const_value(op, as_list=True):
         when as_list=False, return np.array(1), type is <class 'numpy.ndarray'>
         when as_list=True, return 1, type is <class 'int'>.
     """
-    make_sure(is_tf_const_op(op), "{} isn't a const op".format(op.name))
+    make_sure(is_tf_const_op(op), "%r isn't a const op", op.name)
     value = get_tf_tensor_data(op.get_attr("value"))
     if as_list:
         value = value.tolist()
@@ -119,9 +118,6 @@ def map_tf_dtype(dtype):
 
 def get_tf_node_attr(node, name):
     """Parser TF node attribute."""
-    if six.PY2:
-        # For python2, TF get_attr does not accept unicode
-        name = str(name)
     return node.get_attr(name)
 
 
@@ -136,14 +132,14 @@ def tflist_to_onnx(g, shape_override):
     """
 
     # ignore the following attributes
-    ignored_attr = ["unknown_rank", "_class", "Tshape", "use_cudnn_on_gpu", "Index", "Tpaddings",
+    ignored_attr = {"unknown_rank", "_class", "Tshape", "use_cudnn_on_gpu", "Index", "Tpaddings",
                     "TI", "Tparams", "Tindices", "Tlen", "Tdim", "Tin", "dynamic_size", "Tmultiples",
                     "Tblock_shape", "Tcrops", "index_type", "Taxis", "U", "maxval",
                     "Tout", "Tlabels", "Tindex", "element_shape", "Targmax", "Tperm", "Tcond",
                     "T_threshold", "element_dtype", "shape_type", "_lower_using_switch_merge",
                     "parallel_iterations", "_num_original_outputs", "output_types", "output_shapes",
                     "key_dtype", "value_dtype", "Tin", "Tout", "capacity", "component_types", "shapes",
-                    "Toutput_types"]
+                    "Toutput_types"}
 
     node_list = g.get_operations()
     functions = {}
@@ -176,12 +172,11 @@ def tflist_to_onnx(g, shape_override):
             attr_cnt[a] += 1
             if a == "dtype":
                 attr[a] = map_tf_dtype(get_tf_node_attr(node, "dtype"))
-            elif a in ["T"]:
+            elif a == "T":
                 dtype = get_tf_node_attr(node, a)
-                if dtype:
-                    if not isinstance(dtype, list):
-                        dtypes[node.name] = map_tf_dtype(dtype)
-            elif a in ["output_type", "output_dtype", "out_type", "Tidx", "out_idx"]:
+                if dtype and not isinstance(dtype, list):
+                    dtypes[node.name] = map_tf_dtype(dtype)
+            elif a in {"output_type", "output_dtype", "out_type", "Tidx", "out_idx"}:
                 # Tidx is used by Range
                 # out_idx is used by ListDiff
                 attr[a] = map_tf_dtype(get_tf_node_attr(node, a))
@@ -192,7 +187,7 @@ def tflist_to_onnx(g, shape_override):
             elif a == "output_shapes":
                 # we should not need it since we pull the shapes above already
                 pass
-            elif a in ["body", "cond", "then_branch", "else_branch"]:
+            elif a in {"body", "cond", "then_branch", "else_branch"}:
                 input_shapes = [inp.get_shape() for inp in node.inputs]
                 nattr = get_tf_node_attr(node, a)
                 attr[a] = nattr.name