diff --git a/fairseq/__init__.py b/fairseq/__init__.py
index 4123fcd6f..c5d4b5607 100644
--- a/fairseq/__init__.py
+++ b/fairseq/__init__.py
@@ -7,3 +7,5 @@
 #
 
 from .multiprocessing_pdb import pdb
+
+__all__ = ['pdb']
diff --git a/fairseq/bleu.py b/fairseq/bleu.py
index 13a3bf507..3aec86738 100644
--- a/fairseq/bleu.py
+++ b/fairseq/bleu.py
@@ -97,7 +97,7 @@ class Scorer(object):
     def result_string(self, order=4):
         assert order <= 4, "BLEU scores for order > 4 aren't supported"
         fmt = 'BLEU{} = {:2.2f}, {:2.1f}'
-        for i in range(1, order):
+        for _ in range(1, order):
             fmt += '/{:2.1f}'
         fmt += ' (BP={:.3f}, ratio={:.3f}, syslen={}, reflen={})'
         bleup = [p * 100 for p in self.precision()[:order]]
diff --git a/fairseq/data.py b/fairseq/data.py
index 135648998..baf42bbc8 100644
--- a/fairseq/data.py
+++ b/fairseq/data.py
@@ -326,7 +326,7 @@ def shuffled_batches_by_size(src, dst, max_tokens=None, epoch=1, sample=0, max_p
 
         batches = result
     else:
-        for i in range(epoch - 1):
+        for _ in range(epoch - 1):
             np.random.shuffle(batches)
 
     return batches
diff --git a/fairseq/sequence_generator.py b/fairseq/sequence_generator.py
index e568f2de2..ba284ee11 100644
--- a/fairseq/sequence_generator.py
+++ b/fairseq/sequence_generator.py
@@ -126,7 +126,7 @@ class SequenceGenerator(object):
 
         # helper function for allocating buffers on the fly
         buffers = {}
-        def buffer(name, type_of=tokens):
+        def buffer(name, type_of=tokens):  # noqa
             if name not in buffers:
                 buffers[name] = type_of.new()
             return buffers[name]
diff --git a/fairseq/utils.py b/fairseq/utils.py
index 37bbc9e1d..07225f36e 100644
--- a/fairseq/utils.py
+++ b/fairseq/utils.py
@@ -41,7 +41,7 @@ def torch_persistent_save(*args, **kwargs):
     for i in range(3):
         try:
             return torch.save(*args, **kwargs)
-        except:
+        except Exception:
             if i == 2:
                 logging.error(traceback.format_exc())
 
diff --git a/generate.py b/generate.py
index af490c4fa..91efd7d13 100644
--- a/generate.py
+++ b/generate.py
@@ -1,3 +1,4 @@
+#!/usr/bin/env python3
 # Copyright (c) 2017-present, Facebook, Inc.
 # All rights reserved.
 #
diff --git a/preprocess.py b/preprocess.py
index 8edbaacd5..e46094b20 100644
--- a/preprocess.py
+++ b/preprocess.py
@@ -1,3 +1,4 @@
+#!/usr/bin/env python3
 # Copyright (c) 2017-present, Facebook, Inc.
 # All rights reserved.
 #
diff --git a/score.py b/score.py
index 1d3ba72fd..fc5633882 100644
--- a/score.py
+++ b/score.py
@@ -1,3 +1,4 @@
+#!/usr/bin/env python3
 # Copyright (c) 2017-present, Facebook, Inc.
 # All rights reserved.
 #
diff --git a/setup.py b/setup.py
index bb43387a7..7a2274c12 100644
--- a/setup.py
+++ b/setup.py
@@ -1,3 +1,4 @@
+#!/usr/bin/env python3
 # Copyright (c) 2017-present, Facebook, Inc.
 # All rights reserved.
 #
diff --git a/train.py b/train.py
index 9966608a5..f9ac37206 100644
--- a/train.py
+++ b/train.py
@@ -1,3 +1,4 @@
+#!/usr/bin/env python3
 # Copyright (c) 2017-present, Facebook, Inc.
 # All rights reserved.
 #