Importing the multiarray numpy extension module failed. Most likely you are trying to import a failed build of numpy
i solve it 
my solution was
Run locally   1- python -m pip install python-dev-tools
then  2- pip freeze > requirements.txt
3-git add .
4-git commit -m "v5"
5- heroku git:remote -a "your appname on heroku"
6-git push heroku master
my project run local on pycharm without error but when i deployed it on heroku
 error message appears :Importing the multiarray numpy extension module failed.
 i changed numpy version more than one but it does not work
Django Version:     2.2.5
Exception Type:     ImportError
Exception Value: Importing the multiarray numpy extension module failed.  Most
likely you are trying to import a failed build of numpy.
If you're working with a numpy git repo, try git clean -xdf (removes all
files not under version control).  Otherwise reinstall numpy.
Original error was: libpython3.6m.so.1.0: cannot open shared object file: No such file or directory
Exception Location:     /app/.heroku/python/lib/python3.6/site-packages/numpy/core/init.py in , line 26
Python Executable:  /app/.heroku/python/bin/python
Python Version:     3.6.10
numpy version : 1.18.1
any solution?