Install ipython libraries (Of course, you can skip if already installed.)
> pip install ipython
> pip install nbconvert
Convert single file
> ipython nbconvert ? to script abc.ipynb
You can have abc.py
Convert multi files
> ipython nbconvert ? to script abc.ipynb def.ipynb
abc.py, def.py
> ipython nbconvert ? to script *.ipynb
abc.py, def.py
All done!
Have a good day ^^