Versions:

• Anaconda3 5.2.0
• Python 3.6.5
• opencv-python 3.4.9.31

This blog might be out of date soon, but the method introduced will last for a long time.

1. Download Anaconda

Previous versions of Anaconda are available in the archive(click to check). Considering the computer system, I choose to download Anaconda3-5.2.0-Windows-x86_64.exe including Python3.6.5 since python36 is more stable than python37, so we need not to install python again.

2. Install Anaconda

Steps are shown on https://docs.anaconda.com/anaconda/install/windows/.
After installation, run Anaconda Navigator, it can be seen that console_shortcut, Spyder and Jupyter notebook have been installed as well.

3. Install two packages —— numpy(necessary), matplotlib(optional)

Launch console_shortcut, type codes:

pip install numpy
1

Similarly, matplotlib can be installed by typing codes:

pip install matplotlib
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4. Install opencv-python

Considering stablility, I choose to install opencv3.x by continuing to type codes in console_shortcut:

pip install opencv-python==3.4.9.31
1

Available versions can all be seen and downloaded from the website:
https://pypi.org/project/opencv-python/#history
By the way, installed packages can be checked by typing pip list.

5. Test

Launch Spyder in Anaconda Navigator, type in

import cv2
print(cv2.__version__)
1
2

click$\,$"Run"$\,$button.

The result is shown in the picture.

Plus

Overview of Spyder :

Spyder is a powerful scientific environment written in Python, for Python, and designed by and for scientists, engineers and data analysts. It offers a unique combination of the advanced editing, analysis, debugging, and profiling functionality of a comprehensive development tool with the data exploration, interactive execution, deep inspection, and beautiful visualization capabilities of a scientific package.

In terms of data processing and analyzing, Spyder is better than PyCharm(another popular python IDLE).