Use f-strings where sensible

pyproject.toml

@@ -79,6 +79,7 @@ extend-select = [
     "F63",
     "F7",
     "F82",
+    "FLY",  # flynt
     "I",
     "S", # Bandit
     "UP",

src/paho/mqtt/client.py

@@ -338,7 +338,7 @@ def wait_for_publish(self, timeout=None):
         elif self.rc == MQTT_ERR_AGAIN:
             pass
         elif self.rc > 0:
-            raise RuntimeError('Message publish failed: %s' % (error_string(self.rc)))
+            raise RuntimeError(f'Message publish failed: {error_string(self.rc)}')
 
         timeout_time = None if timeout is None else time_func() + timeout
         timeout_tenth = None if timeout is None else timeout / 10.
@@ -357,7 +357,7 @@ def is_published(self):
         elif self.rc == MQTT_ERR_AGAIN:
             pass
         elif self.rc > 0:
-            raise RuntimeError('Message publish failed: %s' % (error_string(self.rc)))
+            raise RuntimeError(f'Message publish failed: {error_string(self.rc)}')
 
         with self._condition:
             return self._published
@@ -515,7 +515,7 @@ def __init__(self, client_id="", clean_session=None, userdata=None,
 
         if transport.lower() not in ('websockets', 'tcp'):
             raise ValueError(
-                'transport must be "websockets" or "tcp", not %s' % transport)
+                f'transport must be "websockets" or "tcp", not {transport}')
         self._manual_ack = manual_ack
         self._transport = transport.lower()
         self._protocol = protocol
@@ -923,17 +923,17 @@ def connect_srv(self, domain=None, keepalive=60, bind_address="",
             domain = domain[domain.find('.') + 1:]
 
         try:
-            rr = '_mqtt._tcp.%s' % domain
+            rr = f'_mqtt._tcp.{domain}'
             if self._ssl:
                 # IANA specifies secure-mqtt (not mqtts) for port 8883
-                rr = '_secure-mqtt._tcp.%s' % domain
+                rr = f'_secure-mqtt._tcp.{domain}'
             answers = []
             for answer in dns.resolver.query(rr, dns.rdatatype.SRV):
                 addr = answer.target.to_text()[:-1]
                 answers.append(
                     (addr, answer.port, answer.priority, answer.weight))
         except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer, dns.resolver.NoNameservers) as err:
-            raise ValueError("No answer/NXDOMAIN for SRV in %s" % domain) from err
+            raise ValueError(f"No answer/NXDOMAIN for SRV in {domain}") from err
 
         # FIXME: doesn't account for weight
         for answer in answers:
@@ -2808,8 +2808,10 @@ def _send_connect(self, keepalive):
             proto_ver |= 0x80
 
         self._pack_remaining_length(packet, remaining_length)
-        packet.extend(struct.pack("!H" + str(len(protocol)) + "sBBH", len(protocol), protocol, proto_ver, connect_flags,
-                                  keepalive))
+        packet.extend(struct.pack(
+            f"!H{len(protocol)}sBBH",
+            len(protocol), protocol, proto_ver, connect_flags, keepalive,
+        ))
 
         if self._protocol == MQTTv5:
             packet += packed_connect_properties
@@ -3273,7 +3275,7 @@ def _handle_disconnect(self):
 
     def _handle_suback(self):
         self._easy_log(MQTT_LOG_DEBUG, "Received SUBACK")
-        pack_format = "!H" + str(len(self._in_packet['packet']) - 2) + 's'
+        pack_format = f"!H{len(self._in_packet['packet']) - 2}s"
         (mid, packet) = struct.unpack(pack_format, self._in_packet['packet'])
 
         if self._protocol == MQTTv5:
@@ -3283,7 +3285,7 @@ def _handle_suback(self):
             for c in packet[props_len:]:
                 reasoncodes.append(ReasonCodes(SUBACK >> 4, identifier=c))
         else:
-            pack_format = "!" + "B" * len(packet)
+            pack_format = f"!{'B' * len(packet)}"
             granted_qos = struct.unpack(pack_format, packet)
 
         with self._callback_mutex:
@@ -3315,9 +3317,9 @@ def _handle_publish(self):
         message.qos = (header & 0x06) >> 1
         message.retain = (header & 0x01)
 
-        pack_format = "!H" + str(len(self._in_packet['packet']) - 2) + 's'
+        pack_format = f"!H{len(self._in_packet['packet']) - 2}s"
         (slen, packet) = struct.unpack(pack_format, self._in_packet['packet'])
-        pack_format = '!' + str(slen) + 's' + str(len(packet) - slen) + 's'
+        pack_format = f"!{slen}s{len(packet) - slen}s"
         (topic, packet) = struct.unpack(pack_format, packet)
 
         if self._protocol != MQTTv5 and len(topic) == 0:
@@ -3330,12 +3332,12 @@ def _handle_publish(self):
         try:
             print_topic = topic.decode('utf-8')
         except UnicodeDecodeError:
-            print_topic = "TOPIC WITH INVALID UTF-8: " + str(topic)
+            print_topic = f"TOPIC WITH INVALID UTF-8: {topic!r}"
 
         message.topic = topic
 
         if message.qos > 0:
-            pack_format = "!H" + str(len(packet) - 2) + 's'
+            pack_format = f"!H{len(packet) - 2}s"
             (message.mid, packet) = struct.unpack(pack_format, packet)
 
         if self._protocol == MQTTv5:

src/paho/mqtt/properties.py

@@ -259,7 +259,7 @@ def __setattr__(self, name, value):
             # the name could have spaces in, or not.  Remove spaces before assignment
             if name not in [aname.replace(' ', '') for aname in self.names.keys()]:
                 raise MQTTException(
-                    "Property name must be one of "+str(self.names.keys()))
+                    f"Property name must be one of {self.names.keys()}")
             # check that this attribute applies to the packet type
             if self.packetType not in self.properties[self.getIdentFromName(name)][1]:
                 raise MQTTException(f"Property {name} does not apply to packet type {PacketTypes.Names[self.packetType]}")
@@ -269,23 +269,20 @@ def __setattr__(self, name, value):
                 if name in ["ReceiveMaximum", "TopicAlias"] \
                         and (value < 1 or value > 65535):
 
-                    raise MQTTException(
-                        "%s property value must be in the range 1-65535" % (name))
+                    raise MQTTException(f"{name} property value must be in the range 1-65535")
                 elif name in ["TopicAliasMaximum"] \
                         and (value < 0 or value > 65535):
 
-                    raise MQTTException(
-                        "%s property value must be in the range 0-65535" % (name))
+                    raise MQTTException(f"{name} property value must be in the range 0-65535")
                 elif name in ["MaximumPacketSize", "SubscriptionIdentifier"] \
                         and (value < 1 or value > 268435455):
 
-                    raise MQTTException(
-                        "%s property value must be in the range 1-268435455" % (name))
+                    raise MQTTException(f"{name} property value must be in the range 1-268435455")
                 elif name in ["RequestResponseInformation", "RequestProblemInformation", "PayloadFormatIndicator"] \
                         and (value != 0 and value != 1):
 
                     raise MQTTException(
-                        "%s property value must be 0 or 1" % (name))
+                        f"{name} property value must be 0 or 1")
 
             if self.allowsMultiple(name):
                 if not isinstance(value, list):
@@ -302,8 +299,7 @@ def __str__(self):
             if hasattr(self, compressedName):
                 if not first:
                     buffer += ", "
-                buffer += compressedName + " : " + \
-                    str(getattr(self, compressedName))
+                buffer += f"{compressedName} : {getattr(self, compressedName)}"
                 first = False
         buffer += "]"
         return buffer
@@ -422,6 +418,6 @@ def unpack(self, buffer):
             compressedName = propname.replace(' ', '')
             if not self.allowsMultiple(compressedName) and hasattr(self, compressedName):
                 raise MQTTException(
-                    "Property '%s' must not exist more than once" % property)
+                    f"Property '{property}' must not exist more than once")
             setattr(self, propname, value)
         return self, propslen + VBIlen

src/paho/mqtt/subscribeoptions.py

@@ -63,7 +63,7 @@ def __init__(self, qos=0, noLocal=False, retainAsPublished=False, retainHandling
     def __setattr__(self, name, value):
         if name not in self.names:
             raise MQTTException(
-                name + " Attribute name must be one of "+str(self.names))
+                f"{name} Attribute name must be one of {self.names}")
         object.__setattr__(self, name, value)
 
     def pack(self):

tests/mqtt5_props.py

@@ -42,18 +42,18 @@ def gen_uint32_prop(identifier, word):
 
 def gen_string_prop(identifier, s):
     s = s.encode("utf-8")
-    prop = struct.pack('!BH%ds'%(len(s)), identifier, len(s), s)
+    prop = struct.pack(f'!BH{len(s)}s', identifier, len(s), s)
     return prop
 
 def gen_string_pair_prop(identifier, s1, s2):
     s1 = s1.encode("utf-8")
     s2 = s2.encode("utf-8")
-    prop = struct.pack('!BH%dsH%ds'%(len(s1), len(s2)), identifier, len(s1), s1, len(s2), s2)
+    prop = struct.pack(f'!BH{len(s1)}sH{len(s2)}s', identifier, len(s1), s1, len(s2), s2)
     return prop
 
 def gen_varint_prop(identifier, val):
     v = pack_varint(val)
-    return struct.pack("!B"+str(len(v))+"s", identifier, v)
+    return struct.pack(f"!B{len(v)}s", identifier, v)
 
 def pack_varint(varint):
     s = b""

tests/paho_test.py

@@ -87,14 +87,13 @@ def expect_packet(sock, name, expected):
 
 def packet_matches(name, recvd, expected):
     if recvd != expected:
-        print("FAIL: Received incorrect " + name + ".")
+        print(f"FAIL: Received incorrect {name}.")
         try:
-            print("Received: " + to_string(recvd))
+            print(f"Received: {to_string(recvd)}")
         except struct.error:
-            print("Received (not decoded): 0x" +
-                  binascii.b2a_hex(recvd).decode('utf8'))
+            print(f"Received (not decoded): 0x{binascii.b2a_hex(recvd).decode('utf8')}")
         try:
-            print("Expected: " + to_string(expected))
+            print(f"Expected: {to_string(expected)}")
         except struct.error:
             print("Expected (not decoded): 0x" +
                   binascii.b2a_hex(expected).decode('utf8'))
@@ -163,7 +162,7 @@ def do_client_connect(connect_packet, connack_packet, hostname="localhost", port
 
 def remaining_length(packet):
     l = min(5, len(packet))  # noqa: E741
-    all_bytes = struct.unpack("!" + "B" * l, packet[:l])
+    all_bytes = struct.unpack(f"!{'B' * l}", packet[:l])
     mult = 1
     rl = 0
     for i in range(1, l - 1):
@@ -195,7 +194,7 @@ def to_string(packet):
     if len(packet) == 0:
         return ""
 
-    packet0 = struct.unpack("!B%ds" % (len(packet)-1), bytes(packet))
+    packet0 = struct.unpack(f"!B{len(packet) - 1}s", bytes(packet))
     packet0 = packet0[0]
     cmd = packet0 & 0xF0
     if cmd == 0x00:
@@ -388,7 +387,7 @@ def mqtt_read_string(sock, rl):
     slen = sock.recv(2)
     slen, = struct.unpack("!H", slen)
     payload = sock.recv(slen)
-    payload, = struct.unpack("!%ds" % (slen), payload)
+    payload, = struct.unpack(f"!{slen}s", payload)
     rl -= (2 + slen)
     return (payload, rl)