Using Python 3.7 with libmapper

[Filipe Calegario]

Hello people,

The workshop today was really nice!

I just got inspired to start a project with Python 3 and libmapper. However, I got some errors.

What I did:

git clone https://github.com/libmapper/libmapper.git

cd libmapper

I've used the flag:

./autogen.sh PYTHON=python3

make 

make install

cd swig

python3 test.py

and got the following error:

Traceback (most recent call last):

  File "test.py", line 4, in <module>

    import sys, mapper

  File "/Users/fcac/git/libmapper/swig/mapper.py", line 15, in <module>

    import _mapper

ImportError: dlopen(/Users/fcac/git/libmapper/swig/_mapper.so, 2): Symbol not found: _PyClass_Type

  Referenced from: /Users/fcac/git/libmapper/swig/_mapper.so

  Expected in: flat namespace

 in /Users/fcac/git/libmapper/swig/_mapper.so 

However, if I run it with Python 2.7, with 
python test.py it runs perfectly.

Am I missing something? Is that a common error? Quick fix?

Thank you!

Cheers!

Filipe Calegario

filipecalegario.net

[Stephen Sinclair]

I'm unable to try on mac right now, but I can confirm that I'm able to
compile and run for python3.6 and python3.8 on Linux.
Not sure what's going on, but in principle it should work.

regards,
Steve

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[Max Graf]

+1 on this, especially as Python 2 support will be dropped next January. I tried the same procedure with Python 3.8.3 and got the same error message.

Regards,

Max

[Joseph Malloch]

Hi Filipe – if you ran autogen.sh without the PYTHON=python3 argument and built libmapper at some earlier point, the copywhich script may be copying an old python2 library instead. Try running:

make clean

and then repeat your previous steps.

Let us know if this works for you!

Joe

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[Stephen Sinclair]

Oh wow I completely forgot about that script, good thinking Joe.

I just tried compiling for python2 and then python3 and it indeed gives an error, but a different one (on linux):

$ LD_LIBRARY_PATH=../src/.libs/ python3 test.py

Traceback (most recent call last):
  File "test.py", line 4, in <module>
    import sys, mapper

  File "/home/sinclairs/projects/maint/libmapper/swig/mapper.py", line 15, in <module>
    import _mapper
ImportError: /home/sinclairs/projects/maint/libmapper/swig/_mapper.so: undefined symbol: _Py_ZeroStruct

It also absolutely chooses the wrong one:

$ ls build/
lib.linux-x86_64-2.7  lib.linux-x86_64-3.6  temp.linux-x86_64-2.7  temp.linux-x86_64-3.6

$ ./copywhich.sh python3 _mapper
build/lib.linux-x86_64-2.7/_mapper.so

I suppose the "copywhich.sh" script should be replaced, but in the meantime I provided a fix on master.

$ sh ./copywhich.sh python2 _mapper
build/lib.linux-x86_64-2.7/_mapper.so

$ sh ./copywhich.sh python3 _mapper
build/lib.linux-x86_64-3.6/_mapper.cpython-36m-x86_64-linux-gnu.so

Steve

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