diff --git a/src/ssh_audit/algorithms.py b/src/ssh_audit/algorithms.py
index c36275c..7c9a850 100644
--- a/src/ssh_audit/algorithms.py
+++ b/src/ssh_audit/algorithms.py
@@ -1,7 +1,7 @@
 """
    The MIT License (MIT)
 
-   Copyright (C) 2017-2020 Joe Testa (jtesta@positronsecurity.com)
+   Copyright (C) 2017-2021 Joe Testa (jtesta@positronsecurity.com)
    Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
@@ -55,7 +55,7 @@ class Algorithms:
         if self.ssh1kex is None:
             return None
         item = Algorithms.Item(1, SSH1_KexDB.ALGORITHMS)
-        item.add('key', [u'ssh-rsa1'])
+        item.add('key', ['ssh-rsa1'])
         item.add('enc', self.ssh1kex.supported_ciphers)
         item.add('aut', self.ssh1kex.supported_authentications)
         return item
diff --git a/src/ssh_audit/fingerprint.py b/src/ssh_audit/fingerprint.py
index cae1768..a9d2caf 100644
--- a/src/ssh_audit/fingerprint.py
+++ b/src/ssh_audit/fingerprint.py
@@ -1,7 +1,7 @@
 """
    The MIT License (MIT)
 
-   Copyright (C) 2017-2020 Joe Testa (jtesta@positronsecurity.com)
+   Copyright (C) 2017-2021 Joe Testa (jtesta@positronsecurity.com)
    Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
@@ -33,11 +33,11 @@ class Fingerprint:
     @property
     def md5(self) -> str:
         h = hashlib.md5(self.__fpd).hexdigest()
-        r = u':'.join(h[i:i + 2] for i in range(0, len(h), 2))
-        return u'MD5:{}'.format(r)
+        r = ':'.join(h[i:i + 2] for i in range(0, len(h), 2))
+        return 'MD5:{}'.format(r)
 
     @property
     def sha256(self) -> str:
         h = base64.b64encode(hashlib.sha256(self.__fpd).digest())
         r = h.decode('ascii').rstrip('=')
-        return u'SHA256:{}'.format(r)
+        return 'SHA256:{}'.format(r)
diff --git a/src/ssh_audit/gextest.py b/src/ssh_audit/gextest.py
index 47efbce..f82a856 100644
--- a/src/ssh_audit/gextest.py
+++ b/src/ssh_audit/gextest.py
@@ -86,14 +86,14 @@ class GEXTest:
 
         # Check if the server supports any of the group-exchange
         # algorithms.  If so, test each one.
-        for gex_alg in GEX_ALGS:
+        for gex_alg, kex_group_class in GEX_ALGS.items():
             if gex_alg in kex.kex_algorithms:
                 out.d('Preparing to perform DH group exchange using ' + gex_alg + '...', write_now=True)
 
                 if GEXTest.reconnect(out, s, kex, gex_alg) is False:
                     break
 
-                kex_group = GEX_ALGS[gex_alg]()
+                kex_group = kex_group_class()
                 smallest_modulus = -1
 
                 # First try a range of weak sizes.
diff --git a/src/ssh_audit/kexdh.py b/src/ssh_audit/kexdh.py
index 9c4e08a..536f0a8 100644
--- a/src/ssh_audit/kexdh.py
+++ b/src/ssh_audit/kexdh.py
@@ -1,7 +1,7 @@
 """
    The MIT License (MIT)
 
-   Copyright (C) 2017-2020 Joe Testa (jtesta@positronsecurity.com)
+   Copyright (C) 2017-2021 Joe Testa (jtesta@positronsecurity.com)
    Copyright (C) 2017 Andris Raugulis (moo@arthepsy.eu)
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
@@ -37,8 +37,8 @@ from ssh_audit.ssh_socket import SSH_Socket
 
 class KexDH:  # pragma: nocover
     def __init__(self, kex_name: str, hash_alg: str, g: int, p: int) -> None:
-        self.__kex_name = kex_name
-        self.__hash_alg = hash_alg
+        self.__kex_name = kex_name  # pylint: disable=unused-private-member
+        self.__hash_alg = hash_alg  # pylint: disable=unused-private-member
         self.__g = 0
         self.__p = 0
         self.__q = 0
@@ -46,10 +46,10 @@ class KexDH:  # pragma: nocover
         self.__e = 0
         self.set_params(g, p)
 
-        self.__ed25519_pubkey: Optional[bytes] = None
+        self.__ed25519_pubkey: Optional[bytes] = None  # pylint: disable=unused-private-member
         self.__hostkey_type: Optional[bytes] = None
-        self.__hostkey_e = 0
-        self.__hostkey_n = 0
+        self.__hostkey_e = 0  # pylint: disable=unused-private-member
+        self.__hostkey_n = 0  # pylint: disable=unused-private-member
         self.__hostkey_n_len = 0  # Length of the host key modulus.
         self.__ca_n_len = 0  # Length of the CA key modulus (if hostkey is a cert).
 
@@ -121,11 +121,11 @@ class KexDH:  # pragma: nocover
 
         # The public key exponent.
         hostkey_e, hostkey_e_len, ptr = KexDH.__get_bytes(hostkey, ptr)
-        self.__hostkey_e = int(binascii.hexlify(hostkey_e), 16)
+        self.__hostkey_e = int(binascii.hexlify(hostkey_e), 16)  # pylint: disable=unused-private-member
 
         # Here is the modulus size & actual modulus of the host key public key.
         hostkey_n, self.__hostkey_n_len, ptr = KexDH.__get_bytes(hostkey, ptr)
-        self.__hostkey_n = int(binascii.hexlify(hostkey_n), 16)
+        self.__hostkey_n = int(binascii.hexlify(hostkey_n), 16)  # pylint: disable=unused-private-member
 
         # If this is an RSA certificate, continue parsing to extract the CA
         # key.
diff --git a/src/ssh_audit/policy.py b/src/ssh_audit/policy.py
index 77be4c2..fd9d2c7 100644
--- a/src/ssh_audit/policy.py
+++ b/src/ssh_audit/policy.py
@@ -1,7 +1,7 @@
 """
    The MIT License (MIT)
 
-   Copyright (C) 2020 Joe Testa (jtesta@positronsecurity.com)
+   Copyright (C) 2020-2021 Joe Testa (jtesta@positronsecurity.com)
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
@@ -117,7 +117,7 @@ class Policy:
 
         if policy_file is not None:
             try:
-                with open(policy_file, "r") as f:
+                with open(policy_file, "r", encoding='utf-8') as f:
                     policy_data = f.read()
             except FileNotFoundError:
                 print("Error: policy file not found: %s" % policy_file)
@@ -425,8 +425,8 @@ macs = %s
         server_policy_names = []
         client_policy_names = []
 
-        for policy_name in Policy.BUILTIN_POLICIES:
-            if Policy.BUILTIN_POLICIES[policy_name]['server_policy']:
+        for policy_name, policy in Policy.BUILTIN_POLICIES.items():
+            if policy['server_policy']:
                 server_policy_names.append(policy_name)
             else:
                 client_policy_names.append(policy_name)
diff --git a/src/ssh_audit/ssh1_publickeymessage.py b/src/ssh_audit/ssh1_publickeymessage.py
index 037d4a3..67c4dec 100644
--- a/src/ssh_audit/ssh1_publickeymessage.py
+++ b/src/ssh_audit/ssh1_publickeymessage.py
@@ -90,7 +90,7 @@ class SSH1_PublicKeyMessage:
     @property
     def supported_ciphers(self) -> List[str]:
         ciphers = []
-        for i in range(len(SSH1.CIPHERS)):
+        for i in range(len(SSH1.CIPHERS)):  # pylint: disable=consider-using-enumerate
             if self.__supported_ciphers_mask & (1 << i) != 0:
                 ciphers.append(Utils.to_text(SSH1.CIPHERS[i]))
         return ciphers
diff --git a/src/ssh_audit/ssh_audit.py b/src/ssh_audit/ssh_audit.py
index d9da4f4..38b5095 100755
--- a/src/ssh_audit/ssh_audit.py
+++ b/src/ssh_audit/ssh_audit.py
@@ -563,7 +563,7 @@ def make_policy(aconf: AuditConf, banner: Optional['Banner'], kex: Optional['SSH
     # Open with mode 'x' (creates the file, or fails if it already exist).
     succeeded = True
     try:
-        with open(aconf.policy_file, 'x') as f:
+        with open(aconf.policy_file, 'x', encoding='utf-8') as f:
             f.write(policy_data)
     except FileExistsError:
         succeeded = False
@@ -681,7 +681,7 @@ def process_commandline(out: OutputBuffer, args: List[str], usage_cb: Callable[.
 
     # If a file containing a list of targets was given, read it.
     if aconf.target_file is not None:
-        with open(aconf.target_file, 'r') as f:
+        with open(aconf.target_file, 'r', encoding='utf-8') as f:
             aconf.target_list = f.readlines()
 
         # Strip out whitespace from each line in target file, and skip empty lines.
@@ -869,10 +869,10 @@ def audit(out: OutputBuffer, aconf: AuditConf, sshv: Optional[int] = None, print
                 if len(payload) > 0:
                     payload_txt = payload.decode('utf-8')
                 else:
-                    payload_txt = u'empty'
+                    payload_txt = 'empty'
             except UnicodeDecodeError:
-                payload_txt = u'"{}"'.format(repr(payload).lstrip('b')[1:-1])
-            if payload_txt == u'Protocol major versions differ.':
+                payload_txt = '"{}"'.format(repr(payload).lstrip('b')[1:-1])
+            if payload_txt == 'Protocol major versions differ.':
                 if sshv == 2 and aconf.ssh1:
                     ret = audit(out, aconf, 1)
                     out.write()
@@ -972,8 +972,8 @@ def algorithm_lookup(out: OutputBuffer, alg_names: str) -> int:
     similar_algorithms = [
         alg_unknown + " --> (" + alg_type + ") " + alg_name
         for alg_unknown in algorithms_not_found
-        for alg_type in adb
-        for alg_name in adb[alg_type]
+        for alg_type, alg_names in adb.items()
+        for alg_name in alg_names
         # Perform a case-insensitive comparison using 'casefold'
         # and match substrings using the 'in' operator.
         if alg_unknown.casefold() in alg_name.casefold()
diff --git a/src/ssh_audit/ssh_socket.py b/src/ssh_audit/ssh_socket.py
index 3891588..6853c1c 100644
--- a/src/ssh_audit/ssh_socket.py
+++ b/src/ssh_audit/ssh_socket.py
@@ -338,6 +338,6 @@ class SSH_Socket(ReadBuf, WriteBuf):
 
     def __cleanup(self) -> None:
         self._close_socket(self.__sock)
-        for fd in self.__sock_map:
-            self._close_socket(self.__sock_map[fd])
+        for sock in self.__sock_map.values():
+            self._close_socket(sock)
         self.__sock = None
diff --git a/src/ssh_audit/writebuf.py b/src/ssh_audit/writebuf.py
index 05760b5..5f25d8c 100644
--- a/src/ssh_audit/writebuf.py
+++ b/src/ssh_audit/writebuf.py
@@ -54,7 +54,7 @@ class WriteBuf:
         return self.write(v)
 
     def write_list(self, v: List[str]) -> 'WriteBuf':
-        return self.write_string(u','.join(v))
+        return self.write_string(','.join(v))
 
     @classmethod
     def _bitlength(cls, n: int) -> int: