print function in python not works called by julia through PyCall

[ywlds]

The print function inside a python function when called by a julia function through PyCall seems not "print" anything at all? How can I fixed it, so that when used Julia and Python, we can debug more interactively?

[stevengj]

Works for me:

julia> PyCall.py"print(\"Hello world\")"
Hello world

Are you running in a different environment, like a Jupyter notebook? You may have a problem from the fact that Python's stdio streams are not the same as Julia's, so they might not be captured by the notebook.

[marcpabst]

I can confirm that this does not work in a Jupyter notebook. Any workarounds?

[stevengj]

It's just buffering. pyimport("sys").stdout.flush() causes the output to appear in Jupyter.

[stevengj]

We can do this automatically with

if isdefined(Main, :IJulia) && IJulia.inited
    Main.IJulia.push_postexecute_hook(() -> pyimport("sys")."stdout"."flush"())
end

Maybe we should do this in PyCall's __init__ function?

[marcpabst]

Great, thanks!