pydev console already ex

Question

I get the following error code when trying to run an interactive python console in pydev

I can\'t figure out what is wrong. When I google about the

Answer 1

pip uninstall traitlets just worked for me.

Answer 2

It seems (on my system; YMMV) to be an acknowledged bug where pydev isn't updated to match the API change from ipython version 4 to version 5.

Either do

pip uninstall ipython
pip install ipython==4.2.0

(hinted at in this answer), OR apply the following patch to pydev_ipython_console_011.py.

163c163
<                              self.has_readline)
---
>             )
171d170
<                              use_readline=self.has_readline,
183d181
<                              use_readline=self.has_readline,
194d191
<                              use_readline=self.has_readline,
239,245d235
< 
<         # Only configure readline if we truly are using readline.  IPython can
<         # do tab-completion over the network, in GUIs, etc, where readline
<         # itself may be absent
<         if self.has_readline:
<             self.set_readline_completer()
< 

Uninstalling traitlets allowed me to open the pydev console in eclipse, but broke ipython at the command line, so I reinstalled it. However, since the error message mentioned that some process was dying with exit code 1, I figured there might be a suppressed traceback worth seeing. So, I ran the mentioned command line

/usr/bin/python2.7 -u /home/tsbertalan/eclipse/cpp-mars/eclipse/../../../.p2/pool/plugins/org.python.pydev_4.5.4.201601292234/pysrc/pydevconsole.py 34462 35898 34462 35898

(which obviously depends on my specific installation), and got a traceback ending in

File "/home/tsbertalan/.p2/pool/plugins/org.python.pydev_4.5.4.201601292234/pysrc/_pydev_bundle/pydev_ipython_console_011.py", line 194, in _new_completer_200
    use_readline=self.has_readline,
AttributeError: 'PyDevTerminalInteractiveShell' object has no attribute 'has_readline'

When I googled the last line, I was led to this answer, where it's due to a changed API in ipython v5. So, it's a bug in pydev. I then checked their issue tracker and found it was already handled, and a workaround was to remove offending old API details (see patch above).

Unfortunately, the patch method only works for pydev 4.5.4. When I upgraded using Eclipse's "check for updates" function (in hopes that 5.1.3 would be available--only 5.1.2 was), the patch solved the immediate failure in that the interactive console started, with ipython, but using object? to print docstrings instead printed some sort of dictionary-like object. So, I'm now using pydev 5.1.2 with ipython 4.2.0. Maybe once I get 5.1.3 I'll try updating ipython.