diff --git a/src/DIRAC/ConfigurationSystem/Client/Helpers/Path.py b/src/DIRAC/ConfigurationSystem/Client/Helpers/Path.py
index 11fb2b493a4..7cb2d87aea7 100644
--- a/src/DIRAC/ConfigurationSystem/Client/Helpers/Path.py
+++ b/src/DIRAC/ConfigurationSystem/Client/Helpers/Path.py
@@ -18,7 +18,7 @@ def cfgPath(*args):
     return os.path.normpath(os.path.join(*(str(k) for k in args)))
 
 
-def cfgInstallPath(*args):
+def cfgInstallPath(*args) -> str:
     """
     Path to Installation/Configuration Options
     """
diff --git a/src/DIRAC/DataManagementSystem/DB/FileCatalogComponents/DirectoryMetadata/DirectoryMetadata.py b/src/DIRAC/DataManagementSystem/DB/FileCatalogComponents/DirectoryMetadata/DirectoryMetadata.py
index 5c46db18faf..d6a511a31f9 100644
--- a/src/DIRAC/DataManagementSystem/DB/FileCatalogComponents/DirectoryMetadata/DirectoryMetadata.py
+++ b/src/DIRAC/DataManagementSystem/DB/FileCatalogComponents/DirectoryMetadata/DirectoryMetadata.py
@@ -350,11 +350,8 @@ def getDirectoryMetaParameters(self, dpath, credDict, inherited=True):
             return S_OK({})
         metaDict = {}
         for _dID, key, value in result["Value"]:
-            if key in metaDict:
-                if isinstance(metaDict[key], list):
-                    metaDict[key].append(value)
-                else:
-                    metaDict[key] = [metaDict[key]].append(value)
+            if isinstance(metaDict.get(key), list):
+                metaDict[key].append(value)
             else:
                 metaDict[key] = value
 
diff --git a/src/DIRAC/DataManagementSystem/DB/FileCatalogComponents/FileMetadata/FileMetadata.py b/src/DIRAC/DataManagementSystem/DB/FileCatalogComponents/FileMetadata/FileMetadata.py
index 5b5a248362e..3738866aba5 100644
--- a/src/DIRAC/DataManagementSystem/DB/FileCatalogComponents/FileMetadata/FileMetadata.py
+++ b/src/DIRAC/DataManagementSystem/DB/FileCatalogComponents/FileMetadata/FileMetadata.py
@@ -358,11 +358,8 @@ def __getFileMetaParameters(self, fileID, credDict):
             return S_OK({})
         metaDict = {}
         for fileID, key, value in result["Value"]:
-            if key in metaDict:
-                if isinstance(metaDict[key], list):
-                    metaDict[key].append(value)
-                else:
-                    metaDict[key] = [metaDict[key]].append(value)
+            if isinstance(metaDict.get(key), list):
+                metaDict[key].append(value)
             else:
                 metaDict[key] = value
 
diff --git a/src/DIRAC/FrameworkSystem/Client/ComponentInstaller.py b/src/DIRAC/FrameworkSystem/Client/ComponentInstaller.py
index 6578596c98f..e6933518836 100644
--- a/src/DIRAC/FrameworkSystem/Client/ComponentInstaller.py
+++ b/src/DIRAC/FrameworkSystem/Client/ComponentInstaller.py
@@ -65,6 +65,7 @@
 import subprocess
 from diraccfg import CFG
 from prompt_toolkit import prompt
+from typing import cast
 
 import DIRAC
 from DIRAC import rootPath
@@ -170,7 +171,7 @@ def __init__(self):
         gLogger.debug("DIRAC Root Path =", rootPath)
 
         self.mysqlMode = ""
-        self.localCfg = None
+        self.localCfg: CFG = None
         self.cfgFile = ""
         self.setup = ""
         self.instance = ""
@@ -1364,10 +1365,20 @@ def setupSite(self, scriptCfg, cfg=None):
 
         # Now get the necessary info from self.localCfg
         setupSystems = self.localCfg.getOption(cfgInstallPath("Systems"), ["Configuration", "Framework"])
+
         setupDatabases = self.localCfg.getOption(cfgInstallPath("Databases"), [])
-        setupServices = [k.split("/") for k in self.localCfg.getOption(cfgInstallPath("Services"), [])]
-        setupAgents = [k.split("/") for k in self.localCfg.getOption(cfgInstallPath("Agents"), [])]
-        setupExecutors = [k.split("/") for k in self.localCfg.getOption(cfgInstallPath("Executors"), [])]
+        setupServices = [
+            k.split("/")
+            for k in self.localCfg.getOption(cfgInstallPath("Services"), [])  # pylint: disable=not-an-iterable
+        ]
+        setupAgents = [
+            k.split("/")
+            for k in self.localCfg.getOption(cfgInstallPath("Agents"), [])  # pylint: disable=not-an-iterable
+        ]
+        setupExecutors = [
+            k.split("/")
+            for k in self.localCfg.getOption(cfgInstallPath("Executors"), [])  # pylint: disable=not-an-iterable
+        ]
         setupWeb = self.localCfg.getOption(cfgInstallPath("WebPortal"), False)
         setupConfigurationMaster = self.localCfg.getOption(cfgInstallPath("ConfigurationMaster"), False)
         setupPrivateConfiguration = self.localCfg.getOption(cfgInstallPath("PrivateConfiguration"), False)
@@ -1382,7 +1393,7 @@ def setupSite(self, scriptCfg, cfg=None):
                     DIRAC.exit(-1)
                 return S_ERROR(error)
             serviceSysInstance = serviceTuple[0]
-            if serviceSysInstance not in setupSystems:
+            if serviceSysInstance not in setupSystems:  # pylint: disable=unsupported-membership-test
                 setupSystems.append(serviceSysInstance)
 
         for agentTuple in setupAgents:
@@ -1393,7 +1404,7 @@ def setupSite(self, scriptCfg, cfg=None):
                     DIRAC.exit(-1)
                 return S_ERROR(error)
             agentSysInstance = agentTuple[0]
-            if agentSysInstance not in setupSystems:
+            if agentSysInstance not in setupSystems:  # pylint: disable=unsupported-membership-test
                 setupSystems.append(agentSysInstance)
 
         for executorTuple in setupExecutors:
@@ -1404,7 +1415,7 @@ def setupSite(self, scriptCfg, cfg=None):
                     DIRAC.exit(-1)
                 return S_ERROR(error)
             executorSysInstance = executorTuple[0]
-            if executorSysInstance not in setupSystems:
+            if executorSysInstance not in setupSystems:  # pylint: disable=unsupported-membership-test
                 setupSystems.append(executorSysInstance)
 
         # And to find out the available extensions
@@ -1521,7 +1532,7 @@ def setupSite(self, scriptCfg, cfg=None):
         # info to be propagated, this may cause the later self.setup to fail
         if setupAddConfiguration:
             gLogger.notice("Registering System instances")
-            for system in setupSystems:
+            for system in setupSystems:  # pylint: disable=not-an-iterable
                 self.addSystemInstance(system, self.instance, self.setup, True)
             for system, service in setupServices:
                 if not self.addDefaultOptionsToCS(None, "service", system, service, extensions, overwrite=True)["OK"]:
@@ -1570,7 +1581,7 @@ def setupSite(self, scriptCfg, cfg=None):
                 return result
             dbDict = result["Value"]
 
-            for dbName in setupDatabases:
+            for dbName in setupDatabases:  # pylint: disable=not-an-iterable
                 gLogger.verbose("Setting up database", dbName)
                 if dbName not in installedDatabases:
                     result = self.installDatabase(dbName)
diff --git a/src/DIRAC/ResourceStatusSystem/scripts/dirac_rss_query_dtcache.py b/src/DIRAC/ResourceStatusSystem/scripts/dirac_rss_query_dtcache.py
index a616153df08..0df80307717 100755
--- a/src/DIRAC/ResourceStatusSystem/scripts/dirac_rss_query_dtcache.py
+++ b/src/DIRAC/ResourceStatusSystem/scripts/dirac_rss_query_dtcache.py
@@ -43,10 +43,12 @@ def parseSwitches():
     args = Script.getPositionalArgs()
     if not args:
         error("Missing mandatory 'query' argument")
+        DIRACExit(1)
     elif not args[0].lower() in ("select", "add", "delete"):
         error("Missing mandatory argument")
-    else:
-        query = args[0].lower()
+        DIRACExit(1)
+
+    query = args[0].lower()
 
     switches = dict(Script.getUnprocessedSwitches())