Pip doesn't work with PyDev in Pleiades

Python3 development often uses PyDev, which was initially introduced in Eclipse 2019-09 (Pleiades All in One Eclipse). PyDev allows you to manage and install libraries with pip, but it may not work well in the initial state of Pleiades.

As a specific symptom, enter an arbitrary command in "Command to execute (X)" of "Window (W)> Settings (P)> PyDev> Interpreter> Python Interpreter> Manage with pip" and "Execute". When you press "(R)", "FINISHED" is displayed immediately, but nothing actually happens. For example, even if you execute "install numpy", "numpy" will not be installed, and of course you will not be able to do development work.

As a result of various investigations, it seems that pip is not installed correctly in Python used by Pleiades. So, I reinstalled pip, and now I can operate pip from PyDev.

How to install __pip (for Python3): __

Download get-pip.py from official pip documentation and install it anywhere.
Run get-pip.py in the Python used by Pleiades: <PLEIADES_INSTALL_DIR> \ python \ 3 \ python get-pip.py
After restarting Eclipse, open "Window (W)> Settings (P)> PyDev> Interpreter> Python Interpreter> Python3" and add 3 libraries including "Package" tab pip. You should be able to see that it has been done. Now you can use pip from PyDev.