diff --git a/examples/query_vin_and_stats.py b/examples/query_vin_and_stats.py
index 1dc181c57639f2..c1d58d0a17000d 100755
--- a/examples/query_vin_and_stats.py
+++ b/examples/query_vin_and_stats.py
@@ -12,7 +12,7 @@
 
 def get_current_data_for_pid(pid):
   # 01 xx = Show current data
-  isotp_send(panda, b"\x01"+ (chr(pid)).encode("utf8"), 0x7e0)
+  isotp_send(panda, b"\x01"+ bytes([pid]), 0x7e0)
   return isotp_recv(panda, 0x7e8)
 
 def get_supported_pids():
diff --git a/python/isotp.py b/python/isotp.py
index ac0f8c4a5414a1..ca518a06bcc93d 100644
--- a/python/isotp.py
+++ b/python/isotp.py
@@ -6,7 +6,7 @@ def msg(x):
   if DEBUG:
     print("S:", binascii.hexlify(x))
   if len(x) <= 7:
-    ret = chr(len(x)).encode("utf8") + x
+    ret = bytes([len(x)]) + x
   else:
     assert False
   return ret.ljust(8, b"\x00")
@@ -40,7 +40,7 @@ def isotp_recv_subaddr(panda, addr, bus, sendaddr, subaddr):
     dat = msg[3:]
 
     # 0 block size?
-    CONTINUE = chr(subaddr).encode("utf8") + b"\x30" + b"\x00"*6
+    CONTINUE = bytes([subaddr]) + b"\x30" + b"\x00"*6
     panda.can_send(sendaddr, CONTINUE, bus)
 
     idx = 1
@@ -68,22 +68,22 @@ def isotp_send(panda, x, addr, bus=0, recvaddr=None, subaddr=None):
   if len(x) <= 7 and subaddr is None:
     panda.can_send(addr, msg(x), bus)
   elif len(x) <= 6 and subaddr is not None:
-    panda.can_send(addr, chr(subaddr).encode("utf8") + msg(x)[0:7], bus)
+    panda.can_send(addr, bytes([subaddr]) + msg(x)[0:7], bus)
   else:
     if subaddr:
-      ss = (chr(subaddr) + chr(0x10 + (len(x)>>8)) + chr(len(x)&0xFF)).encode("utf8") + x[0:5]
+      ss = bytes([subaddr]) + bytes([0x10 + (len(x) >> 8)]) + bytes([len(x) & 0xFF]) + x[0:5]
       x = x[5:]
     else:
-      ss = (chr(0x10 + (len(x)>>8)) + chr(len(x)&0xFF)).encode("utf8") + x[0:6]
+      ss = bytes([0x10 + (len(x) >> 8)]) + bytes([len(x) & 0xFF]) + x[0:6]
       x = x[6:]
     idx = 1
     sends = []
     while len(x) > 0:
       if subaddr:
-        sends.append((((chr(subaddr) + chr(0x20 + (idx&0xF))).encode('utf8') + x[0:6]).ljust(8, b"\x00")))
+        sends.append(((bytes([subaddr]) + bytes([0x20 + (idx & 0xF)]) + x[0:6]).ljust(8, b"\x00")))
         x = x[6:]
       else:
-        sends.append(((chr(0x20 + (idx&0xF)).encode("utf8") + x[0:7]).ljust(8, b"\x00")))
+        sends.append(((bytes([0x20 + (idx & 0xF)]) + x[0:7]).ljust(8, b"\x00")))
         x = x[7:]
       idx += 1
 
@@ -107,7 +107,7 @@ def isotp_recv(panda, addr, bus=0, sendaddr=None, subaddr=None):
   else:
     msg = recv(panda, 1, addr, bus)[0]
 
-    if msg[0]&0xf0 == 0x10:
+    if msg[0] & 0xf0 == 0x10:
       # first
       tlen = ((msg[0] & 0xf) << 8) | msg[1]
       dat = msg[2:]