Import ROOT, Error: Failed to import libcppyy3_7. Please check that ROOT has been built for Python 3.7

[bshi]

Dear experts,

I download a pre-compiled binary distribution ROOT6.28.04 and install it in Ubuntu 18.04.

Then I write the configuration file as follows:

# root6
  export ROOTSYS="/mnt/work/soft/root6.28.04/"
  export PATH="$PATH:$ROOTSYS/bin"
  export PYTHONDIR=$ROOTSYS
  export LD_LIBRARY_PATH=$ROOTSYS/lib:$PYTHONDIR/lib:$ROOTSYS/bindings/pyroot:$LD_LIBRARY_PATH
  export PYTHONPATH=$ROOTSYS/lib:$PYTHONPATH:$ROOTSYS/bindings/pyroot
 
 alias root="source /mnt/work/soft/root6.28.04/bin/thisroot.sh && root"

 20 # >>> conda initialize >>>
  __conda_setup="$('/mnt/public/shuangli/anaconda3/bin/conda' 'shell.bash' 'hook' 2> /dev/null)"
 if [ $? -eq 0 ]; then
 eval "$__conda_setup"
 else
 if [ -f "/mnt/public/shuangli/anaconda3/etc/profile.d/conda.sh" ]; then
 .  "/mnt/public/shuangli/anaconda3/etc/profile.d/conda.sh"
 else
 export PATH="/mnt/public/shuangli/anaconda3/bin:$PATH"
   fi
 fi
 unset __conda_setup
 # <<< conda initialize <<<
 
 conda deactivate
 conda activate my_env

When I import the ROOT, an error is given:

  import ROOT
  File "/mnt/work/soft/root6.28.04/lib/ROOT/__init__.py", line 25, in <module>
    import cppyy
  File "/mnt/work/soft/root6.28.04/lib/cppyy/__init__.py", line 64, in <module>
    libcppyy_mod_name, major, minor))
ImportError: Failed to import libcppyy3_7. Please check that ROOT has been built for Python 3.7

After checking, namely root-config --python-version, the python version is 3.6.9, which is different from my python 3.7.16.

My question is why is the version of python inconsistent when I do this?

With best respect,
Boan

[bshi]

By the way, installing ROOT via conda is an alternative way, but the time is too long.

[moneta]

Hi,
The problem is the incompatibility of the Python versions. Try building ROOT from source or install it via Conda

Lorenzo

[bshi]

Thank you, Lorenzo!

The situation is exactly as you mentioned.

In order to clarify for others how the problem can be solved, I’ll explain my specific situation here.

I use someone else’s miniconda, and the python in the base environment is 3.6.9. Therefore, even though I have install python 3.7.16 in my new environment, importing pre-compiled ROOT applies the older python version.

According to this, my solution is formulated as follows:

1: Use my own miniconda.
2: Install ROOT via conda. Following the tutorial, use conda config --set channel_priority strict to dramatically accelerate the entire installation process.
3: Check the environment and the version of python. It must be the same, otherwise it will give you an error like mine.

The above is the experience of a python beginner.

Boan