diff --git a/.travis.yml b/.travis.yml
index 4ca3f5a46..afa59d7b6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -18,10 +18,10 @@ addons:
       - python3-dev
 
 before_install:
-  -  python --version
-  -  pip --version
-  -  sudo pip install -U virtualenv pre-commit pip
+  -  sudo pip3 install -U virtualenv pre-commit pip
   -  docker pull paddlepaddle/paddle:latest
+  -  python3 --version
+  -  pip3 --version
 
 script:
   - exit_code=0
diff --git a/decoders/decoders_deprecated.py b/decoders/decoders_deprecated.py
index 4298e0e1e..0dad44c4a 100644
--- a/decoders/decoders_deprecated.py
+++ b/decoders/decoders_deprecated.py
@@ -120,7 +120,7 @@ def ctc_beam_search_decoder(probs_seq,
             prob_idx = prob_idx[0:cutoff_len]
 
         for l in prefix_set_prev:
-            if not prefix_set_next.has_key(l):
+            if l not in prefix_set_next:
                 probs_b_cur[l], probs_nb_cur[l] = 0.0, 0.0
 
             # extend prefix by travering prob_idx
@@ -134,7 +134,7 @@ def ctc_beam_search_decoder(probs_seq,
                     last_char = l[-1]
                     new_char = vocabulary[c]
                     l_plus = l + new_char
-                    if not prefix_set_next.has_key(l_plus):
+                    if l_plus not in prefix_set_next:
                         probs_b_cur[l_plus], probs_nb_cur[l_plus] = 0.0, 0.0
 
                     if new_char == last_char:
@@ -161,7 +161,7 @@ def ctc_beam_search_decoder(probs_seq,
 
         ## store top beam_size prefixes
         prefix_set_prev = sorted(
-            prefix_set_next.iteritems(), key=lambda asd: asd[1], reverse=True)
+            prefix_set_next.items(), key=lambda asd: asd[1], reverse=True)
         if beam_size < len(prefix_set_prev):
             prefix_set_prev = prefix_set_prev[:beam_size]
         prefix_set_prev = dict(prefix_set_prev)