Getting "SyntaxError: invalid syntax" with ipython2 notebook

Question

With a recent upgrade I am now running into a serious problem with SyntaxError: invalid syntax when starting a python2.7 instance of the notebook with $ ipython2 notebook.

The error seems to originate through tornado which uses ayncio and in that library there is python3.4 syntax.

I can start with $ ipython3 notebook, but the application I am doing is using mayavi which I believe is still for python2 only.

The nasty error message is:

$ ipython2 notebook
Traceback (most recent call last):
  File "/usr/local/bin/ipython2", line 11, in <module>
    sys.exit(start_ipython())
  File "/usr/local/lib/python2.7/dist-packages/IPython/__init__.py", line 118, in start_ipython
    return launch_new_instance(argv=argv, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/traitlets/config/application.py", line 591, in launch_instance
    app.initialize(argv)
  File "<string>", line 2, in initialize
  File "/usr/local/lib/python2.7/dist-packages/traitlets/config/application.py", line 75, in catch_config_error
    return method(app, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/IPython/terminal/ipapp.py", line 305, in initialize
    super(TerminalIPythonApp, self).initialize(argv)
  File "<string>", line 2, in initialize
  File "/usr/local/lib/python2.7/dist-packages/traitlets/config/application.py", line 75, in catch_config_error
    return method(app, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/IPython/core/application.py", line 386, in initialize
    self.parse_command_line(argv)
  File "/usr/local/lib/python2.7/dist-packages/IPython/terminal/ipapp.py", line 300, in parse_command_line
    return super(TerminalIPythonApp, self).parse_command_line(argv)
  File "<string>", line 2, in parse_command_line
  File "/usr/local/lib/python2.7/dist-packages/traitlets/config/application.py", line 75, in catch_config_error
    return method(app, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/traitlets/config/application.py", line 487, in parse_command_line
    return self.initialize_subcommand(subc, subargv)
  File "<string>", line 2, in initialize_subcommand
  File "/usr/local/lib/python2.7/dist-packages/traitlets/config/application.py", line 75, in catch_config_error
    return method(app, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/traitlets/config/application.py", line 418, in initialize_subcommand
    subapp = import_item(subapp)
  File "/usr/local/lib/python2.7/dist-packages/ipython_genutils/importstring.py", line 31, in import_item
    module = __import__(package, fromlist=[obj])
  File "/usr/local/lib/python2.7/dist-packages/notebook/notebookapp.py", line 48, in <module>
    from tornado import httpserver
  File "/usr/local/lib/python2.7/dist-packages/tornado/httpserver.py", line 34, in <module>
    from tornado.http1connection import HTTP1ServerConnection, HTTP1ConnectionParameters
  File "/usr/local/lib/python2.7/dist-packages/tornado/http1connection.py", line 28, in <module>
    from tornado import gen
  File "/usr/local/lib/python2.7/dist-packages/tornado/gen.py", line 1236, in <module>
    import tornado.platform.asyncio
  File "/usr/local/lib/python2.7/dist-packages/tornado/platform/asyncio.py", line 33, in <module>
    import asyncio
  File "/usr/local/lib/python2.7/dist-packages/asyncio/__init__.py", line 9, in <module>
    from . import selectors
  File "/usr/local/lib/python2.7/dist-packages/asyncio/selectors.py", line 39
    "{!r}".format(fileobj)) from None
                               ^
SyntaxError: invalid syntax

What would help in my sitation? Downgrading tornado? Is there something wrong in my setup. Why is it at all possible to install asyncio under python2.7?

Answer 1

Downgrading tornado works:

$ sudo pip install tornado==4.1
$ ipython2 notebook
[I 17:22:31.800 NotebookApp] Serving notebooks from local directory: /home/fnielsen/fnielsen/ipynb
...