Cannot get started on OSX

[sglyon]

I am a Python developer and have multiple working versions of Python on my machine.

I cannot, however, get PyCall to work after simply following the instructions from the readme and doing Pkg.add("PyCall"). This is what a sample session looks like:

julia> using PyCall

julia> @pyimport scipy.optimize as so
ERROR: could not load module /libpython2.7.dylib: dlopen(/libpython2.7.dylib.dylib, 9): image not found
 in pyinitialize at /Users/sglyon/.julia/PyCall/src/PyCall.jl:339
 in pyimport at /Users/sglyon/.julia/PyCall/src/PyCall.jl:105

The error message is fairly clear at explaining what is happening, but I have no idea why PyCall is looking for python at / or how I tell it where my Python is. I would like to use the python at ~/anaconda/bin/python. I tried to be more explicit and set $PYTHONHOME to various values near that directory. I have tried all of the below values:

• export PYTHONHOME="/Users/sglyon/anaconda/lib/python2.7"
• export PYTHONHOME="/Users/sglyon/anaconda/bin"
• export PYTHONHOME="/Users/sglyon/anaconda/lib/"
• export PYTHONHOME="/Users/sglyon/anaconda/"

For each of those values I get the following printout (it is the same for any of the listed values):

julia> using PyCall

julia> @pyimport scipy.optimize as so
ImportError: No module named site
ERROR: failed process: Process(`python -c "import distutils.sysconfig; print(distutils.sysconfig.get_config_var('LDLIBRARY'))"`, ProcessExited(1)) [1]
 in error at error.jl:22
 in pipeline_error at process.jl:436
 in readall at process.jl:394
 in libpython_name at /Users/sglyon/.julia/PyCall/src/PyCall.jl:328
 in pyinitialize at /Users/sglyon/.julia/PyCall/src/PyCall.jl:339
 in pyimport at /Users/sglyon/.julia/PyCall/src/PyCall.jl:105

What other configuration do I need to do to get this to work with the python of my choosing? (Note that the anaconda python is the first on my$PATH and is executing when typing python from the command line.)

[stevengj]

As a workaround, you can run

using PyCall
pyinitialize("/....path..../libpython2.7.dylib")

to specify the Python shared library to link to.

Currently, PyCall runs the python executable and executes:

import distutils.sysconfig
print(distutils.sysconfig.get_config_var('LDLIBRARY'))
print(distutils.sysconfig.get_config_var('PYTHONFRAMEWORKPREFIX'))

to find out the name and location of the Python library. What does this print for you?

Alternatively, I'm thinking of using python-config instead. What does python-config --ldflags print for you?

[AlexMikhalev]

Same problem, but I am using anaconda,

workaround

using PyCall
pyinitialize("/opt/anaconda/lib/libpython2.7.dylib")

worked, but

In [1]: import distutils.sysconfig

In [2]: print(distutils.sysconfig.get_config_var('LDLIBRARY'))
libpython2.7.dylib

In [3]: print(distutils.sysconfig.get_config_var('PYTHONFRAMEWORKPREFIX'))

In [4]: 

[sglyon]

@stevengj, thanks for the quick response. The pyinitialize(path) also worked for me!

FYI, when I run the commands listed (the ones PyCall executes) I get the exact same thing as @AlexMikhalev:

In [1]: import distutils.sysconfig

In [2]: print(distutils.sysconfig.get_config_var('LDLIBRARY'))
libpython2.7.dylib

In [3]: print(distutils.sysconfig.get_config_var('PYTHONFRAMEWORKPREFIX'))


In [4]: 

Executing python-config --ldflags gives the following (I get the feeling that this isn't what you want):

➜  ~  python-config --ldflags 
-ldl -framework CoreFoundation -lpython2.7 -u _PyMac_Error

[stevengj]

Hmm, those --ldflags seem broken if that is what ~/anaconda/bin/python-config is printing, since that doesn't specify the location of the python2.7 library.

I need a way to query the location of libpython from either python or python-config...

[sglyon]

Hmm. I'll think about it and let you know if I can come up with anything.

[lindahua]

I believe this works (at least for Mac OS X):

# get the path of (default) python executable
exepath = readchomp(`python -c "import sys; print sys.executable"`)   

 # construct the path of libpython
libpath = joinpath(dirname(dirname(exepath)), "lib", "libpython2.7.dylib")  

[stevengj]

@lindahua, that works, and I can also use pyconfigvar(python, "LIBDIR") as well. However, I tried this with Anaconda and I got another error:

Could not find platform independent libraries <prefix>
Could not find platform dependent libraries <exec_prefix>
Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>]
ImportError: No module named site

With other Python installations I never had to set PYTHONHOME manually, so I'm not sure what is going on here.

[stevengj]

Hmm, looks like I need to send the full path of the Python executable (via sys.executable) to Py_SetProgramName.