pip3: command not found

Writing the whole path/directory eg. (for windows) C:\Programs\Python\Python36-32\Scripts\pip3.exe install mypackage. This worked well for me when I had trouble with pip.

You would need to install pip3.

On Linux, run first sudo apt update. Then the command would be: sudo apt install python3-pip

On Mac, using brew, first brew install python3
Then brew postinstall python3

Try calling pip3 -V to see if it worked.

I had this issue and I fixed it using the following steps You need to completely uninstall python3-pip using:

sudo apt-get --purge autoremove python3-pip

Then resintall the package with:

 sudo apt install python3-pip

To confirm that everything works, run:

 pip3 -V

After this you can now use pip3 to manage any python package of your interest. Eg

pip3 install NumPy