Running a twisted sample script on Python 3.7 (macOS) raises exception

问题

I'm tryign to have twisted 19.7.0 running on macOS Catalina 10.15.1 with Python 3.7.5.

I choose the chat sample to verify if it works (see source chat.py in https://twistedmatrix.com/documents/current/core/howto/servers.html).

Following documentation I've installed twisted using virtualenv.

I start the script and then I test it with telnet:

telnet 127.0.0.1 8123

It follows the stacktrace:

Unhandled Error
Traceback (most recent call last):
  File "/Users/giacomo/.virtualenvs/twisted-samples/lib/python3.7/site-packages/twisted/python/log.py", line 86, in callWithContext
    return context.call({ILogContext: newCtx}, func, *args, **kw)
  File "/Users/giacomo/.virtualenvs/twisted-samples/lib/python3.7/site-packages/twisted/python/context.py", line 122, in callWithContext
    return self.currentContext().callWithContext(ctx, func, *args, **kw)
  File "/Users/giacomo/.virtualenvs/twisted-samples/lib/python3.7/site-packages/twisted/python/context.py", line 85, in callWithContext
    return func(*args,**kw)
  File "/Users/giacomo/.virtualenvs/twisted-samples/lib/python3.7/site-packages/twisted/internet/selectreactor.py", line 149, in _doReadOrWrite
    why = getattr(selectable, method)()
--- <exception caught here> ---
  File "/Users/giacomo/.virtualenvs/twisted-samples/lib/python3.7/site-packages/twisted/internet/tcp.py", line 1435, in doRead
    protocol.makeConnection(transport)
  File "/Users/giacomo/.virtualenvs/twisted-samples/lib/python3.7/site-packages/twisted/internet/protocol.py", line 514, in makeConnection
    self.connectionMade()
  File "/Users/giacomo/pyenvs/twisted-samples/chat.py", line 13, in connectionMade
    self.sendLine("What's your name?")
  File "/Users/giacomo/.virtualenvs/twisted-samples/lib/python3.7/site-packages/twisted/protocols/basic.py", line 636, in sendLine
    return self.transport.write(line + self.delimiter)
builtins.TypeError: can only concatenate str (not "bytes") to str

Unhandled Error
Traceback (most recent call last):
  File "/Users/giacomo/.virtualenvs/twisted-samples/lib/python3.7/site-packages/twisted/python/log.py", line 103, in callWithLogger
    return callWithContext({"system": lp}, func, *args, **kw)
  File "/Users/giacomo/.virtualenvs/twisted-samples/lib/python3.7/site-packages/twisted/python/log.py", line 86, in callWithContext
    return context.call({ILogContext: newCtx}, func, *args, **kw)
  File "/Users/giacomo/.virtualenvs/twisted-samples/lib/python3.7/site-packages/twisted/python/context.py", line 122, in callWithContext
    return self.currentContext().callWithContext(ctx, func, *args, **kw)
  File "/Users/giacomo/.virtualenvs/twisted-samples/lib/python3.7/site-packages/twisted/python/context.py", line 85, in callWithContext
    return func(*args,**kw)
--- <exception caught here> ---
  File "/Users/giacomo/.virtualenvs/twisted-samples/lib/python3.7/site-packages/twisted/internet/selectreactor.py", line 149, in _doReadOrWrite
    why = getattr(selectable, method)()
  File "/Users/giacomo/.virtualenvs/twisted-samples/lib/python3.7/site-packages/twisted/internet/tcp.py", line 243, in doRead
    return self._dataReceived(data)
  File "/Users/giacomo/.virtualenvs/twisted-samples/lib/python3.7/site-packages/twisted/internet/tcp.py", line 249, in _dataReceived
    rval = self.protocol.dataReceived(data)
  File "/Users/giacomo/.virtualenvs/twisted-samples/lib/python3.7/site-packages/twisted/protocols/basic.py", line 572, in dataReceived
    why = self.lineReceived(line)
  File "/Users/giacomo/pyenvs/twisted-samples/chat.py", line 21, in lineReceived
    self.handle_GETNAME(line)
  File "/Users/giacomo/pyenvs/twisted-samples/chat.py", line 29, in handle_GETNAME
    self.sendLine("Welcome, %s!" % (name,))
  File "/Users/giacomo/.virtualenvs/twisted-samples/lib/python3.7/site-packages/twisted/protocols/basic.py", line 636, in sendLine
    return self.transport.write(line + self.delimiter)
builtins.TypeError: can only concatenate str (not "bytes") to str

My system Python is 2.7.16, version 3 is installed with brew.

If I need to post more info about my system, please let me know.

回答1:

Here's your issue:

    return self.transport.write(line + self.delimiter)
builtins.TypeError: can only concatenate str (not "bytes") to str

You're mixing bytes and string values. What you get from the network is a bytes object and you will have to convert the str to bytes. Also you cannot send str over the network. All sent data must be bytes. So assuming self.delimiter is the a string, you would just need to fix:

return self.transport.write(line + self.delimiter.decode("utf8"))

No need to return on self.transport.write(). And you bring up a point that the docs are geared toward Python 2.7 and some of the examples don't work well for Python3+. This is a bug in my opinion. It's a good opportunity to contribute to Twisted ;)

来源：https://stackoverflow.com/questions/58764784/running-a-twisted-sample-script-on-python-3-7-macos-raises-exception

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