警告：PyPlot 正在使用 tkagg 后端，这会导致 MacOS 上的崩溃

Question

Does anyone knows how to change the backend of PyPlot from "TkAgg" to Qt5Agg in Julia?

I got this warning when I try to Using PyPlot in Julia:

julia> using PyPlot
[ Info: Recompiling stale cache file /Users/tonyspc/.julia/compiled/v1.2/PyPlot/oatAj.ji for PyPlot [d330b81b-6aea-500a-939a-2ce795aea3ee]
┌ Warning: PyPlot is using tkagg backend, which is known to cause crashes on MacOS (#410); use the MPLBACKEND environment variable to request a different backend.
└ @ PyPlot ~/.julia/packages/PyPlot/4wzW1/src/init.jl:192

I tried to use the solution posted here: https://github.com/JuliaPy/PyPlot.jl/issues/454

But it failed:

julia> using PyCall
[ Info: Recompiling stale cache file /Users/tonyspc/.julia/compiled/v1.2/PyCall/GkzkC.ji for PyCall [438e738f-606a-5dbb-bf0a-cddfbfd45ab0]

julia> pyimport_conda("PyQt5", "pyqt")
ERROR: PyError (PyImport_ImportModule

The Python package PyQt5 could not be found by pyimport. Usually this means
that you did not install PyQt5 in the Python version being used by PyCall.

PyCall is currently configured to use the Python version at:

/System/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python

and you should use whatever mechanism you usually use (apt-get, pip, conda,
etcetera) to install the Python package containing the PyQt5 module.

One alternative is to re-configure PyCall to use a different Python
version on your system: set ENV["PYTHON"] to the path/name of the python
executable you want to use, run Pkg.build("PyCall"), and re-launch Julia.

Another alternative is to configure PyCall to use a Julia-specific Python
distribution via the Conda.jl package (which installs a private Anaconda
Python distribution), which has the advantage that packages can be installed
and kept up-to-date via Julia.  As explained in the PyCall documentation,
set ENV["PYTHON"]="", run Pkg.build("PyCall"), and re-launch Julia. Then,
To install the PyQt5 module, you can use `pyimport_conda("PyQt5", PKG)`,
where PKG is the Anaconda package the contains the module PyQt5,
or alternatively you can use the Conda package directly (via
`using Conda` followed by `Conda.add` etcetera).

) <type 'exceptions.ImportError'>
ImportError('No module named PyQt5',)

Stacktrace:
 [1] pyimport(::String) at /Users/tonyspc/.julia/packages/PyCall/ttONZ/src/PyCall.jl:544
 [2] pyimport_conda(::String, ::String, ::String) at /Users/tonyspc/.julia/packages/PyCall/ttONZ/src/PyCall.jl:702
 [3] pyimport_conda(::String, ::String) at /Users/tonyspc/.julia/packages/PyCall/ttONZ/src/PyCall.jl:701
 [4] top-level scope at REPL[4]:1

However I already installed PyQt5 using brew install pyqt

And I don't know why my matplot library is located at python2 directory not the python3 directory:

julia> pyimport("matplotlib").matplotlib_fname()
"/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/mpl-data/matplotlibrc"

I have python2 that comes with default on my Mac, and installed python3 using Homebrew

MacBook-Pro:~ tonyspc$ which python3
/usr/local/bin/python3
MacBook-Pro:~ tonyspc$ which python
/usr/bin/python

Should I set the ENV["PYTHON"] to "/usr/local/bin/python3" ?

Answer 1

I had a similar problem, and I added this to my.bashrc to run every time:

export MPLBACKEND=qt5agg

Then after doing the ]build PyCall PyPlot and restarting julia, it seemed to find the right backend to plot.

My relevant issue I opened (and the answer I got): https://github.com/JuliaPy/PyPlot.jl/issues/453#issuecomment-527163934

Answer 2

Try setting ENV["PYTHON"] = "/usr/local/bin/python3" in a fresh REPL followed by pkg> build PyCall PyPlot . This should make PyCall (and therefore also PyPlot) use your local Python 3.