diff --git a/lib/rucio/common/utils.py b/lib/rucio/common/utils.py
index 2fbe27fe12..3f16b28561 100644
--- a/lib/rucio/common/utils.py
+++ b/lib/rucio/common/utils.py
@@ -578,7 +578,7 @@ def val_to_space_sep_str(vallist):
         else:
             return str(vallist)
     except:
-        return str('')
+        return ''
 
 
 def date_to_str(date):
diff --git a/lib/rucio/core/replica.py b/lib/rucio/core/replica.py
index 93f2384605..d3d016bbd8 100644
--- a/lib/rucio/core/replica.py
+++ b/lib/rucio/core/replica.py
@@ -94,7 +94,7 @@ def get_bad_replicas_summary(rse_expression=None, from_date=None, to_date=None,
             rse_clause.append(models.BadReplicas.rse_id == rse['id'])
 
     if session.bind.dialect.name == 'oracle':
-        to_days = func.trunc(models.BadReplicas.created_at, str('DD'))
+        to_days = func.trunc(models.BadReplicas.created_at, 'DD')
     elif session.bind.dialect.name == 'mysql':
         to_days = func.date(models.BadReplicas.created_at)
     elif session.bind.dialect.name == 'postgresql':
diff --git a/lib/rucio/daemons/conveyor/receiver.py b/lib/rucio/daemons/conveyor/receiver.py
index 5db6badc95..a4336262f0 100644
--- a/lib/rucio/daemons/conveyor/receiver.py
+++ b/lib/rucio/daemons/conveyor/receiver.py
@@ -70,9 +70,9 @@ def on_message(self, frame):
         if 'job_metadata' in msg.keys() \
            and isinstance(msg['job_metadata'], dict) \
            and 'issuer' in msg['job_metadata'].keys() \
-           and str(msg['job_metadata']['issuer']) == str('rucio'):
+           and str(msg['job_metadata']['issuer']) == 'rucio':
 
-            if 'job_state' in msg.keys() and (str(msg['job_state']) != str('ACTIVE') or msg.get('job_multihop', False) is True):
+            if 'job_state' in msg.keys() and (str(msg['job_state']) != 'ACTIVE' or msg.get('job_multihop', False) is True):
                 METRICS.counter('message_rucio').inc()
 
                 self._perform_request_update(msg)
diff --git a/lib/rucio/transfertool/fts3.py b/lib/rucio/transfertool/fts3.py
index 0af3e82c3a..853c57e5ad 100644
--- a/lib/rucio/transfertool/fts3.py
+++ b/lib/rucio/transfertool/fts3.py
@@ -653,7 +653,7 @@ def __init__(self, external_host, request_id, fts_message):
         self._transfer_id = fts_message.get('tr_id').split("__")[-1]
 
         self._file_metadata = fts_message['file_metadata']
-        self._multi_sources = str(fts_message.get('job_metadata', {}).get('multi_sources', '')).lower() == str('true')
+        self._multi_sources = str(fts_message.get('job_metadata', {}).get('multi_sources', '')).lower() == 'true'
         self._src_url = fts_message.get('src_url', None)
         self._dst_url = fts_message.get('dst_url', None)
 
@@ -724,7 +724,7 @@ def __init__(self, external_host, request_id, job_response, file_response, reque
         self._transfer_id = job_response.get('job_id')
 
         self._file_metadata = file_response['file_metadata']
-        self._multi_sources = str(job_response['job_metadata'].get('multi_sources', '')).lower() == str('true')
+        self._multi_sources = str(job_response['job_metadata'].get('multi_sources', '')).lower() == 'true'
         self._src_url = file_response.get('source_surl', None)
         self._dst_url = file_response.get('dest_surl', None)
         self.logger = logging.log