After installing opencv with PIP3, an error is reported when importing CV2 through Python 3, as follows:

 from .cv2 import *
ImportError: numpy.core.multiarray failed to import

Beacuse the version of NumPy library is too low or too high, which is not suitable for the newly installed opencv version
if we use pip to install the latest version of OpenCV, that is, the installation command:

pip3 install opencv-python
pip3 install opencv_contrib-python

It means that the numpy version is too low, so we should install the latest version:

Command: pip3 install -U numpy

After installation, you can import OpenCV