Library and example2.py is not compatible with Python 3

[jeffsf]

On a machine where Python 3 is now default and Python 2 is not installed (Debian and Ubuntu, for example), example2.py fails to run.

So far:

• Python 2 print in example2.py, rather than print()
• TypeError in "stuff"

Traceback (most recent call last):
  File "/home/jeff/devel/tsip/example2.py", line 58, in <module>
    gps_conn.write(tsip.Packet(0x35, 0b00110011, 0b00000011, 0b00000001, 0b00101001))
  File "/home/jeff/venv/tsip/lib/python3.5/site-packages/tsip/hlapi.py", line 178, in write
    super(GPS, self).write(frame(stuff(packet.pack())))
  File "/home/jeff/venv/tsip/lib/python3.5/site-packages/tsip/llapi.py", line 72, in stuff
    return packet.replace(CHR_DLE, CHR_DLE + CHR_DLE)
TypeError: a bytes-like object is required, not 'str'

apparently from config.py which declares those variables as strings.

Python 3.5.3

[mjuenema]

Oh yes, the never ending ASCII vs. bytes vs. unicode issue. Thanks for reporting this.

[GiriMahesh]

Hi @mjuenema,

Could you please let me know, whether this issue is fixed in latest version?

Thanks much.

[mjuenema]

Hi @GiriMahesh, I haven't done any work on python-TSIP for a very long time so there's no change. This is certainly not good but at the moment I simply don't have the time to work on this project.

[user-8472]

This is not a finished solution but for those just trying to get the library working under python3 these changes will get the code running.

diff --git a/tsip/config.py b/tsip/config.py
index b8dbd19..3d86507 100644
--- a/tsip/config.py
+++ b/tsip/config.py
@@ -14,6 +14,11 @@ ETX = 0x03
 CHR_DLE = chr(DLE)
 CHR_ETX = chr(ETX)

+# DLE and ETX as bytes
+bDLE = DLE.to_bytes(1, 'little')
+bETX = ETX.to_bytes(1, 'little')
+

 # Contants for setting bits
 #

diff --git a/tsip/llapi.py b/tsip/llapi.py
index f9bc7d8..3fb7be8 100644
--- a/tsip/llapi.py
+++ b/tsip/llapi.py
@@ -18,7 +18,8 @@ def is_framed(packet):

     """

-    return packet[0] == CHR_DLE and packet[-2] == CHR_DLE and packet[-1] == CHR_ETX
+    #print("is_framed packet[0]: {}".format(packet[0]))
+    return packet[0] == DLE and packet[-2] == DLE and packet[-1] == ETX


 def frame(data):
@@ -35,7 +36,7 @@ def frame(data):
     if is_framed(data):
         raise ValueError('data contains leading DLE and trailing DLE/ETX')
     else:
-        return CHR_DLE + data + CHR_DLE + CHR_ETX
+        return bDLE + data + bDLE + bETX


 def unframe(packet):
@@ -51,7 +52,8 @@ def unframe(packet):
     """

     if is_framed(packet):
-        return packet.lstrip(CHR_DLE).rstrip(CHR_ETX).rstrip(CHR_DLE)
+        #print("unframe lstrip: {}".format(packet.lstrip(bDLE)))
+        return packet.lstrip(bDLE).rstrip(bETX).rstrip(bDLE)
     else:
         raise ValueError('packet does not contain leading DLE and trailing DLE/ETX')

@@ -69,7 +71,7 @@ def stuff(packet):
     if is_framed(packet):
         raise ValueError('packet contains leading DLE and trailing DLE/ETX')
     else:
-        return packet.replace(CHR_DLE, CHR_DLE + CHR_DLE)
+        return packet.replace(bDLE, bDLE + bDLE)



@@ -87,7 +89,7 @@ def unstuff(packet):
     if is_framed(packet):
         raise ValueError('packet contains leading DLE and trailing DLE/ETX')
     else:
-        return packet.replace(CHR_DLE + CHR_DLE, CHR_DLE)
+        return packet.replace(bDLE + bDLE, bDLE)

 class gps(object):
@@ -100,21 +102,23 @@ class gps(object):

     def read(self):

-        packet = ''
+        packet = bytes()
         dle_count = 0

         last_b = None
         while True:
             b = self.conn.read(1)
+            #print("type b {}".format(type(b)))

             if len(b) == 0:
                 return None

-            packet += chr(ord(b))    # Python 3 work-around
+            packet += b

-            if b == CHR_DLE:
+            if b[0] == DLE:
                 dle_count += 1
-            elif b == CHR_ETX and last_b == CHR_DLE and (dle_count % 2) == 0:    # even, because leading DLE is counted!
+            elif b[0] == ETX and last_b[0] == DLE and (dle_count % 2) == 0:    # even, because leading DLE is counted!
+                #print("gps.read(): {}".format(packet))
                 return packet
             else:
                 pass

[mjuenema]

@user-8472 Thanks for the code. As you can see I haven't worked on this project for years. I can even remember where I put my Trimble GPS receivers in the house.

Would you be able to submit a Pull Request for this?