diff --git a/py/desitransfer/common.py b/py/desitransfer/common.py
index d111b6b..37505a5 100644
--- a/py/desitransfer/common.py
+++ b/py/desitransfer/common.py
@@ -35,7 +35,7 @@ def empty_rsync(out):
         ``True`` if there are no files to transfer.
     """
     rr = re.compile(r'(receiving|sent [0-9]+ bytes|total size)')
-    return all([rr.match(l) is not None for l in out.split('\n') if l])
+    return all([rr.match(out_line) is not None for out_line in out.split('\n') if out_line])
 
 
 def new_exposures(out):
@@ -53,8 +53,8 @@ def new_exposures(out):
     """
     e = set()
     e_re = re.compile(r'([0-9]{8})/?')
-    for l in out.split('\n'):
-        m = e_re.match(l)
+    for out_line in out.split('\n'):
+        m = e_re.match(out_line)
         if m is not None:
             e.add(m.groups()[0])
     return e
@@ -126,7 +126,7 @@ def ensure_scratch(directories):
     """
     for d in directories:
         try:
-            l = os.listdir(d)
+            dir_list = os.listdir(d)
         except FileNotFoundError:
             continue
         return d
@@ -144,7 +144,7 @@ def today():
     This formulation, with the offset ``7/24+0.5``, is inherited from previous
     nightwatch transfer scripts.
     """
-    return (dt.datetime.utcnow() - dt.timedelta(7/24+0.5)).strftime('%Y%m%d')
+    return (dt.datetime.utcnow() - dt.timedelta(7 / 24 + 0.5)).strftime('%Y%m%d')
 
 
 def idle_time(start=8, end=12, tz=None):
@@ -191,4 +191,3 @@ def exclude_years(start_year):
         A list suitable for appending to a command.
     """
     return (' '.join([f'--exclude {y:d}*' for y in range(start_year, time.localtime().tm_year)])).split()
-
diff --git a/py/desitransfer/daemon.py b/py/desitransfer/daemon.py
index ca67715..202587a 100644
--- a/py/desitransfer/daemon.py
+++ b/py/desitransfer/daemon.py
@@ -78,11 +78,10 @@ def __init__(self, options):
             self._ini = options.configuration
         self.test = options.test
         self.tape = options.backup
-        getlist = lambda x: x.split(',')
-        getdict = lambda x: dict([tuple(i.split(':')) for i in x.split(',')])
         self.conf = ConfigParser(defaults=os.environ, strict=True,
                                  interpolation=ExtendedInterpolation(),
-                                 converters={'list': getlist, 'dict': getdict})
+                                 converters={'list': lambda x: x.split(','),
+                                             'dict': lambda x: dict([tuple(i.split(':')) for i in x.split(',')])})
         files = self.conf.read(self._ini)
         # assert files[0] == self._ini
         self.sections = [s for s in self.conf.sections()
@@ -183,11 +182,11 @@ def directory(self, d):
         _, out, err = _popen(cmd)
         links = sorted([x for x in out.split('\n') if x])
         if links:
-            for l in links:
-                if self._link_re.search(l) is None:
-                    log.warning("Malformed symlink detected: %s. Skipping.", l)
+            for link in links:
+                if self._link_re.search(link) is None:
+                    log.warning("Malformed symlink detected: %s. Skipping.", link)
                 else:
-                    self.exposure(d, l, status)
+                    self.exposure(d, link, status)
         else:
             log.warning('No links found, check connection.')
         #
@@ -440,9 +439,9 @@ def backup(self, d, night, status):
             if self.tape:
                 log.debug(' '.join(cmd))
                 _, out, err = _popen(cmd)
-                with open(ls_file) as l:
-                    data = l.read()
-                backup_files = [l.split()[-1] for l in data.split('\n') if l]
+                with open(ls_file) as ls_fileobj:
+                    data = ls_fileobj.read()
+                backup_files = [ls_out.split()[-1] for ls_out in data.split('\n') if ls_out]
             else:
                 backup_files = []
             backup_file = hpss_file + '_' + night + '.tar'
@@ -544,9 +543,9 @@ def verify_checksum(checksum_file):
                   checksum_file, n_lines)
         errors += "{0:d} file(s) listed but not downloaded.\n".format(n_lines)
     if n_lines < 0:
-        log.error("%d files are not listed in %s!", -1*n_lines, checksum_file)
-        errors += "{0:d} file(s) downloaded but not listed.\n".format(-1*n_lines)
-    digest = dict([(l.split()[1], l.split()[0]) for l in lines if l])
+        log.error("%d files are not listed in %s!", -1 * n_lines, checksum_file)
+        errors += "{0:d} file(s) downloaded but not listed.\n".format(-1 * n_lines)
+    digest = dict([(cl.split()[1], cl.split()[0]) for cl in lines if cl])
     for f in files:
         ff = os.path.join(d, f)
         if ff != checksum_file:
@@ -668,5 +667,5 @@ def main():
                      options.kill)
             return 0
         transfer.transfer()
-        time.sleep(sleep*60)
+        time.sleep(sleep * 60)
     return 0
diff --git a/py/desitransfer/daily.py b/py/desitransfer/daily.py
index ef67921..c66ec8c 100644
--- a/py/desitransfer/daily.py
+++ b/py/desitransfer/daily.py
@@ -56,14 +56,14 @@ def transfer(self, permission=True):
         if self.extra:
             for i, e in enumerate(self.extra):
                 cmd.insert(cmd.index('--omit-dir-times') + 1 + i, e)
-        with open(self.log, 'ab') as l:
-            l.write(("DEBUG: desi_daily_transfer %s\n" % dtVersion).encode('utf-8'))
-            l.write(("DEBUG: %s\n" % ' '.join(cmd)).encode('utf-8'))
-            l.write(("DEBUG: Transfer start: %s\n" % stamp()).encode('utf-8'))
-            l.flush()
-            p = sub.Popen(cmd, stdout=l, stderr=sub.STDOUT)
+        with open(self.log, 'ab') as logfile:
+            logfile.write(("DEBUG: desi_daily_transfer %s\n" % dtVersion).encode('utf-8'))
+            logfile.write(("DEBUG: %s\n" % ' '.join(cmd)).encode('utf-8'))
+            logfile.write(("DEBUG: Transfer start: %s\n" % stamp()).encode('utf-8'))
+            logfile.flush()
+            p = sub.Popen(cmd, stdout=logfile, stderr=sub.STDOUT)
             status = p.wait()
-            l.write(("DEBUG: Transfer complete: %s\n" % stamp()).encode('utf-8'))
+            logfile.write(("DEBUG: Transfer complete: %s\n" % stamp()).encode('utf-8'))
         if status == 0:
             self.lock()
             if permission:
@@ -80,8 +80,8 @@ def lock(self):
                 fpath = os.path.join(dirpath, f)
                 if stat.S_IMODE(os.stat(fpath).st_mode) != file_perm:
                     os.chmod(fpath, file_perm)
-        with open(self.log, 'ab') as l:
-            l.write(("DEBUG: Lock complete: %s\n" % stamp()).encode('utf-8'))
+        with open(self.log, 'ab') as logfile:
+            logfile.write(("DEBUG: Lock complete: %s\n" % stamp()).encode('utf-8'))
 
     def permission(self):
         """Set permissions for DESI collaboration access.
@@ -95,12 +95,12 @@ def permission(self):
             The status returned by :command:`fix_permissions.sh`.
         """
         cmd = ['fix_permissions.sh', self.destination]
-        with open(self.log, 'ab') as l:
-            l.write(("DEBUG: %s\n" % ' '.join(cmd)).encode('utf-8'))
-            l.flush()
-            p = sub.Popen(cmd, stdout=l, stderr=sub.STDOUT)
+        with open(self.log, 'ab') as logfile:
+            logfile.write(("DEBUG: %s\n" % ' '.join(cmd)).encode('utf-8'))
+            logfile.flush()
+            p = sub.Popen(cmd, stdout=logfile, stderr=sub.STDOUT)
             status = p.wait()
-            l.write(("DEBUG: Permission reset complete: %s\n" % stamp()).encode('utf-8'))
+            logfile.write(("DEBUG: Permission reset complete: %s\n" % stamp()).encode('utf-8'))
         return status
 
 
diff --git a/py/desitransfer/nightwatch.py b/py/desitransfer/nightwatch.py
index e28d4d3..c133623 100644
--- a/py/desitransfer/nightwatch.py
+++ b/py/desitransfer/nightwatch.py
@@ -114,7 +114,7 @@ def main():
     options = _options()
     _configure_log(options.debug)
     errcount = 0
-    wait = options.sleep*60
+    wait = options.sleep * 60
     source = '/exposures/nightwatch'
     basedir = os.path.join(os.environ['DESI_ROOT'], 'spectro', 'nightwatch')
     kpnodir = os.path.join(basedir, 'kpno')
diff --git a/py/desitransfer/test/test_common.py b/py/desitransfer/test/test_common.py
index 46f6dd3..f40f0a0 100644
--- a/py/desitransfer/test/test_common.py
+++ b/py/desitransfer/test/test_common.py
@@ -135,7 +135,7 @@ def test_today(self, mock_dt):
         """Test today's date.
         """
         mock_dt.datetime.utcnow.return_value = datetime(2019, 7, 3, 5, 0, 0)
-        mock_dt.timedelta.return_value = timedelta(7/24+0.5)
+        mock_dt.timedelta.return_value = timedelta(7 / 24 + 0.5)
         y = today()
         self.assertEqual(y, '20190702')
 
diff --git a/py/desitransfer/test/test_daemon.py b/py/desitransfer/test/test_daemon.py
index e7d41a4..783c121 100644
--- a/py/desitransfer/test/test_daemon.py
+++ b/py/desitransfer/test/test_daemon.py
@@ -1045,49 +1045,48 @@ def test_verify_checksum(self):
         d = os.path.dirname(c)
         with patch('os.listdir') as mock_listdir:
             mock_listdir.return_value = ['t.sha256sum', 'test_file_1.txt', 'test_file_2.txt']
-            with patch('desitransfer.daemon.log') as l:
+            with patch('desitransfer.daemon.log') as mock_log:
                 o = verify_checksum(c)
         self.assertEqual(o, "")
-        l.debug.assert_has_calls([call("%s is valid.", os.path.join(d, 'test_file_1.txt')),
-                                  call("%s is valid.", os.path.join(d, 'test_file_2.txt'))])
+        mock_log.debug.assert_has_calls([call("%s is valid.", os.path.join(d, 'test_file_1.txt')),
+                                         call("%s is valid.", os.path.join(d, 'test_file_2.txt'))])
         #
         # Wrong number of files.
         #
         with patch('os.listdir') as mock_listdir:
             mock_listdir.return_value = ['t.sha256sum', 'test_file_1.txt']
-            with patch('desitransfer.daemon.log') as l:
+            with patch('desitransfer.daemon.log') as mock_log:
                 o = verify_checksum(c)
         self.assertEqual(o, "1 file(s) listed but not downloaded.\n")
-        l.error.assert_has_calls([call("%s lists %d file(s) that are not present!", c, 1)])
+        mock_log.error.assert_has_calls([call("%s lists %d file(s) that are not present!", c, 1)])
         with patch('os.listdir') as mock_listdir:
             mock_listdir.return_value = ['t.sha256sum', 'test_file_1.txt', 'test_file_2.txt', 'test_file_3.txt']
-            with patch('desitransfer.daemon.log') as l:
+            with patch('desitransfer.daemon.log') as mock_log:
                 o = verify_checksum(c)
         self.assertEqual(o, "1 file(s) downloaded but not listed.\ntest_file_3.txt not listed in checksum file.\n")
-        l.error.assert_has_calls([call("%d files are not listed in %s!", 1, c)])
+        mock_log.error.assert_has_calls([call("%d files are not listed in %s!", 1, c)])
         #
         # Bad list of files.
         #
         with patch('os.listdir') as mock_listdir:
             mock_listdir.return_value = ['t.sha256sum', 'test_file_1.txt', 'test_file_3.txt']
-            with patch('desitransfer.daemon.log') as l:
+            with patch('desitransfer.daemon.log') as mock_log:
                 o = verify_checksum(c)
         self.assertEqual(o, "test_file_3.txt not listed in checksum file.\n")
-        l.debug.assert_has_calls([call("%s is valid.", os.path.join(d, 'test_file_1.txt'))])
-        l.error.assert_has_calls([call("%s does not appear in %s!", os.path.join(d, 'test_file_3.txt'), c)])
+        mock_log.debug.assert_has_calls([call("%s is valid.", os.path.join(d, 'test_file_1.txt'))])
+        mock_log.error.assert_has_calls([call("%s does not appear in %s!", os.path.join(d, 'test_file_3.txt'), c)])
         #
         # Hack hashlib to produce incorrect checksums.
         #
         with patch('os.listdir') as mock_listdir:
             mock_listdir.return_value = ['t.sha256sum', 'test_file_1.txt', 'test_file_2.txt']
-            with patch('desitransfer.daemon.log') as l:
-                with patch('hashlib.sha256') as h:
-                    # h.sha256 = MagicMock()
-                    h.hexdigest.return_value = 'abcdef'
+            with patch('desitransfer.daemon.log') as mock_log:
+                with patch('hashlib.sha256') as mock_hash:
+                    mock_hash.hexdigest.return_value = 'abcdef'
                     o = verify_checksum(c)
         self.assertEqual(o, "test_file_1.txt had a checksum mismatch.\ntest_file_2.txt had a checksum mismatch.\n")
-        l.error.assert_has_calls([call("Checksum mismatch for %s in %s!", os.path.join(d, 'test_file_1.txt'), c),
-                                  call("Checksum mismatch for %s in %s!", os.path.join(d, 'test_file_2.txt'), c)])
+        mock_log.error.assert_has_calls([call("Checksum mismatch for %s in %s!", os.path.join(d, 'test_file_1.txt'), c),
+                                         call("Checksum mismatch for %s in %s!", os.path.join(d, 'test_file_2.txt'), c)])
 
     @patch('os.walk')
     @patch('os.chmod')
diff --git a/py/desitransfer/test/test_status.py b/py/desitransfer/test/test_status.py
index 8f1a0ed..6cfc073 100644
--- a/py/desitransfer/test/test_status.py
+++ b/py/desitransfer/test/test_status.py
@@ -75,17 +75,17 @@ def test_TransferStatus_init(self):
         # New directory.
         #
         d = '/desi/spectro/status'
-        with patch('desitransfer.status.log') as l:
-            with patch('os.makedirs') as m:
-                with patch('shutil.copy') as cp:
-                    with patch('shutil.copyfile') as cf:
+        with patch('desitransfer.status.log') as mock_log:
+            with patch('os.makedirs') as mock_makedirs:
+                with patch('shutil.copy') as mock_copy:
+                    with patch('shutil.copyfile') as mock_copyfile:
                         s = TransferStatus(d)
-        l.debug.assert_has_calls([call("os.makedirs('%s', exist_ok=True)", d),
-                                  call("shutil.copyfile('%s', '%s')", h, os.path.join(d, 'index.html')),
-                                  call("shutil.copy('%s', '%s')", j, d)])
-        m.assert_called_once_with(d, exist_ok=True)
-        cp.assert_called_once_with(j, d)
-        cf.assert_called_once_with(h, os.path.join(d, 'index.html'))
+        mock_log.debug.assert_has_calls([call("os.makedirs('%s', exist_ok=True)", d),
+                                         call("shutil.copyfile('%s', '%s')", h, os.path.join(d, 'index.html')),
+                                         call("shutil.copy('%s', '%s')", j, d)])
+        mock_makedirs.assert_called_once_with(d, exist_ok=True)
+        mock_copy.assert_called_once_with(j, d)
+        mock_copyfile.assert_called_once_with(h, os.path.join(d, 'index.html'))
 
     @patch('desitransfer.status.log')
     def test_TransferStatus_handle_malformed_with_log(self, mock_log):
diff --git a/py/desitransfer/test/test_top_level.py b/py/desitransfer/test/test_top_level.py
index 22588b4..8393d93 100644
--- a/py/desitransfer/test/test_top_level.py
+++ b/py/desitransfer/test/test_top_level.py
@@ -13,8 +13,7 @@ class TestTopLevel(unittest.TestCase):
 
     @classmethod
     def setUpClass(cls):
-        cls.versionre = re.compile(
-                r'([0-9]+!)?([0-9]+)(\.[0-9]+)*((a|b|rc|\.post|\.dev)[0-9]+)?')
+        cls.versionre = re.compile(r'([0-9]+!)?([0-9]+)(\.[0-9]+)*((a|b|rc|\.post|\.dev)[0-9]+)?')
 
     @classmethod
     def tearDownClass(cls):
diff --git a/py/desitransfer/tucson.py b/py/desitransfer/tucson.py
index 826d601..60524c0 100644
--- a/py/desitransfer/tucson.py
+++ b/py/desitransfer/tucson.py
@@ -241,7 +241,7 @@ def main():
         for s in suffix:
             if options.sleep.endswith(s):
                 try:
-                    sleepy_time = int(options.sleep[0:-1])*suffix[s]
+                    sleepy_time = int(options.sleep[0:-1]) * suffix[s]
                 except ValueError:
                     log.error("Invalid value for sleep interval: '%s'!", options.sleep)
                     return 1
diff --git a/setup.cfg b/setup.cfg
index a5faf6c..3117a46 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -115,9 +115,7 @@ exclude_lines =
 # These are normally ignored by default:
 # ignore = E121, E123, E126, E133, E226, E241, E242, E704, W503, W504
 #
-# In addition to the default set we add:
+# These are the explicitly ignored styles:
 # - E501: line too long (82 > 79 characters)
-# - E731: do not assign a lambda expression, use a def
-# - E741: do not use variables named 'l', 'O', or 'I' -- because, for example,
-#   'l' might refer to Galactic longitude.
-ignore = E121, E123, E126, E133, E226, E241, E242, E501, E704, E731, E741, W503, W504
+# - W504: line break after binary operator
+ignore = E501, W504