clearer error message for default MacOS matplotlib

[trbedwards]

I've imported the PyPlot module like so:
using PyCall
pygui(:tk)
using PyPlot

I then try to use the plot function:
x=1:10; y=sin(x);
plot(x,y)

But I get this error:
pltm not defined
while loading In[14], in expression starting on line 1

in abstract_eval_global at ./inference.jl:1027
in abstract_eval_symbol at ./inference.jl:1066
in abstract_eval at ./inference.jl:919
in abstract_eval_arg at ./inference.jl:866
in abstract_eval_call at ./inference.jl:878
in abstract_eval at ./inference.jl:935
in abstract_eval_arg at ./inference.jl:866
in abstract_eval_call at ./inference.jl:878
in abstract_eval at ./inference.jl:935
in abstract_interpret at ./inference.jl:1107
in typeinf at ./inference.jl:1409
in typeinf at /Users/tre11/git/julia/usr/lib/julia/sys.dylib
in typeinf_ext at ./inference.jl:1216

This is in the latest stable version of Julia 0.3.4-pre+8, and latest stable versions of python, ipython, matpplotlib, etc.

[stevengj]

Works fine for me in both Julia 0.3 and Julia 0.4 on MacOS. Can you try Pkg.checkout("PyCall") and Pkg.checkout("PyPlot") to see if the latest master versions fix this?

[trbedwards]

I've just tried re-compiling julia on the master branch, but now I have this error:
config.status: executing libtool commands
configure: summary of build options:

Version: GNU MP 6.0.0
Host type: x86_64-apple-darwin14.0.0
ABI: 64
Install prefix: /Users/tre11/git/julia/usr
Compiler: clang -stdlib=libc++ -mmacosx-version-min=10.7 -m64
Static libraries: no
Shared libraries: yes

make[1]: *** [julia-release] Error 2
make: *** [release] Error 2

[stevengj]

My suggestion was to check out the master versions of PyPlot and PyCall, not compile the latest Julia. Julia 0.3.x should be fine.

[trbedwards]

So I re-installed Julia (using the latest stable pre-compiled binary for OS X), installed the PyCall and PyPlot packages then checked out the master versions using Pkg.checkout("PyCall") and Pkg.checkout("PyPlot"). I get a slightly different error this time:

ERROR: pltm not defined
in abstract_eval_global at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib
in abstract_eval_symbol at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib
in abstract_eval at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib
in abstract_eval_arg at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib
in abstract_eval_call at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib
in abstract_eval at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib
in abstract_eval_arg at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib
in abstract_eval_call at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib
in abstract_eval at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib
in abstract_interpret at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib
in typeinf at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib (repeats 2 times)
in abstract_call_gf at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib
in abstract_call at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib (repeats 2 times)
in abstract_eval_call at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib
in abstract_eval at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib
in abstract_eval_arg at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib
in typeinf at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib (repeats 2 times)
in typeinf_ext at /Applications/Julia-0.3.3.app/Contents/Resources/julia/lib/julia/sys.dylib

I should also add that when I importing the PyPlot module with using PyPlot I get the following error:
Warning: error initializing module PyPlot: PyCall.PyError(msg="PyImport_ImportModule", T=PyCall.PyObject(o=0x00000000118dd698), val=PyCall.PyObject(o=0x0000000013d914d0), traceback=PyCall.PyObject(o=0x0000000013d7fdd0))

[trbedwards]

Ok so I managed to get rid of the errors by installing qt with brew install qt then entering pygui(:qt) after using PyCall. However, when I plot something, nothing appears. Is there some further setting up I need to do to display the plot? I've tried both in julia and ipython console --profile julia. Thanks

[stevengj]

What happens if you do

using PyCall
pyimport("matplotlib.pyplot")

?

[stevengj]

(BTW, I tend to recommend Anaconda Python rather than Homebrew; I've found Homebrew to be rather fragile for Python packages.)

[trbedwards]

I got it working like this:

using PyCall
@pyimport matplotlib.pyplot as plt
plt.plot(x,y)
plt.show()

[trbedwards]

Thanks a lot, just a quick question. Is there a way to select the plot window after it's been generated? If I focus on another application then I cannot cmd-tab to the plot window unless I click and drag other windows out of the way. Sometime I lose the window and have to restart julia.

[stevengj]

@trbedwards, @pyimport matplotlib.pyplot as plt is working because it defaults to the MacOS (Cocoa) backend. (No, I don't know how to force it to bring the plot window to the front; maybe file an issue with Matplotlib, assuming the same thing happens in Python.)

You'd ideally like to get PyPlot working in order to get interactive plots (so that you don't need show and can use the REPL and the plot window simultaneously) or for IJulia. However, PyPlot doesn't support the native MacOS backend (see #11), so you have to have a Python with a working Tk or Qt GUI backend for Matplotlib.

Unfortunately, the Matplotlib that ships with MacOS doesn't have a working Qt or Tk backend as far as I can tell, so you need to install a different Matplotlib to use the PyPlot module. I recommend installing Anaconda Python (which will give you Matplotlib, SciPy, etc.).

[stevengj]

Actually, I looked into this further, and it seems that the Tk backend does work with the built-in Matplotlib in MacOS, but it requires that you install XQuartz.

So, just install XQuartz and PyPlot should work.

Re-opening since we should really have a clearer error message for this.