diff --git a/quantecon/__init__.py b/quantecon/__init__.py
index b88d762fb..fabf9ab27 100644
--- a/quantecon/__init__.py
+++ b/quantecon/__init__.py
@@ -7,10 +7,10 @@
 
 try:
     import numba
-except:
+except ImportError as e:
     raise ImportError(
-        "Cannot import numba from current anaconda distribution. \
-            Please run `conda install numba` to install the latest version.")
+        "Cannot import numba, which QuantEcon.py requires. Install it with "
+        "`pip install numba` or `conda install numba`.") from e
 
 #-Modules-#
 from . import distributions
diff --git a/quantecon/_dle.py b/quantecon/_dle.py
index ceeaee7f1..7bafed20d 100644
--- a/quantecon/_dle.py
+++ b/quantecon/_dle.py
@@ -243,7 +243,7 @@ def compute_sequence(self, x0, ts_length=None, Pay=None):
 
         # === Value of asset whose payout vector is Pay*xt === #
         # See p.145: Equation (7.11.1)
-        if isinstance(Pay, np.ndarray) == True:
+        if isinstance(Pay, np.ndarray):
             self.Za = Pay.T @ self.Mc
             self.Q = solve_discrete_lyapunov(
                 self.A0.T * self.beta**0.5, self.Za)
@@ -277,7 +277,7 @@ def irf(self, ts_length=100, shock=None):
 
         """
 
-        if type(shock) != np.ndarray:
+        if not isinstance(shock, np.ndarray):
             # Default is to select first element of w
             shock = np.vstack((np.ones((1, 1)), np.zeros((self.nw - 1, 1))))
 
diff --git a/quantecon/game_theory/game_generators/__init__.py b/quantecon/game_theory/game_generators/__init__.py
index fa20a29ea..1b51543b5 100644
--- a/quantecon/game_theory/game_generators/__init__.py
+++ b/quantecon/game_theory/game_generators/__init__.py
@@ -1,6 +1,11 @@
-# flake8: noqa
 """
 game_theory.game_generators
 
 """
-from .bimatrix_generators import *
+from .bimatrix_generators import (blotto_game, ranking_game, sgc_game,
+                                  tournament_game, unit_vector_game)
+
+__all__ = [
+    'blotto_game', 'ranking_game', 'sgc_game', 'tournament_game',
+    'unit_vector_game'
+]
diff --git a/quantecon/tests/test_graph_tools.py b/quantecon/tests/test_graph_tools.py
index 00e20b526..222c27ef9 100644
--- a/quantecon/tests/test_graph_tools.py
+++ b/quantecon/tests/test_graph_tools.py
@@ -134,7 +134,7 @@ def setup_method(self):
         for graph_dict in self.graphs.graph_dicts:
             try:
                 weighted = graph_dict['weighted']
-            except:
+            except KeyError:
                 weighted = False
             graph_dict['g'] = DiGraph(graph_dict['A'], weighted=weighted)
 
diff --git a/quantecon/tests/test_quadsum.py b/quantecon/tests/test_quadsum.py
index 60011b6c6..2843144bd 100644
--- a/quantecon/tests/test_quadsum.py
+++ b/quantecon/tests/test_quadsum.py
@@ -53,11 +53,3 @@ def test_m_matsum():
         summedval = summedval + a**i * b * a.T**i
 
     assert_allclose(retval, summedval, atol=1e-5, rtol=0)
-
-
-
-if __name__ == '__main__':
-    test_simplesum()
-    test_identitysum()
-    test_m_simplesum()
-    test_m_identitysum
diff --git a/quantecon/util/notebooks.py b/quantecon/util/notebooks.py
index 37b0f1bf4..5dc60e51d 100644
--- a/quantecon/util/notebooks.py
+++ b/quantecon/util/notebooks.py
@@ -86,7 +86,7 @@ def fetch_nb_dependencies(files, repo=REPO, raw=RAW, branch=BRANCH, folder=FOLDE
     import requests
 
     #-Generate Common Data Structure-#
-    if type(files) == list:
+    if isinstance(files, list):
         files = {"" : files}
 
     status = []
diff --git a/quantecon/util/timing.py b/quantecon/util/timing.py
index f415e23c8..83c125051 100644
--- a/quantecon/util/timing.py
+++ b/quantecon/util/timing.py
@@ -247,7 +247,7 @@ def __enter__(self):
         self._start_time = time.time()
         return self
         
-    def __exit__(self, exc_type, exc_val, exc_tb):
+    def __exit__(self, *exc_info):
         end_time = time.time()
         self.elapsed = end_time - self._start_time