Install opencv environment for raspberry pie to solve no module named 'CV2'

lately On raspberry pie install opencv For days   Introduce my methods and solutions

The current raspberry pie system Built in python2 and python3

therefore   When the system is installed Using the command line Input : python Will be output The default version number is 2.7.X

however everyone open Thonny Will find   The output bar shows python yes 3.7.X   .    And the current raspberry pie system 2020 Years later, it has stopped right python2 For maintenance （ Heard online ）

because Before the installation opencv It has always been aimed at python Installed , So there will be mistakes , Report errors python3 import cv2 Error indication NO module named 'cv2’

Now let me introduce my solutions and installation methods , But it takes a long time , need 5-6 Hours

1. First take Raspberry pie is the default py2 Change it to py3 ,py3 Don't download it again , because The system comes with

Modify using the following command  

udo update-alternatives --install /usr/bin/ python python /usr/bin/ python2 100

sudo update-alternatives --install /usr/bin/ python python /usr/bin/ python3 150

2. Then according to the article of this link According to py3 Of opencv Installation method installation , But there will be mistakes

https://www.jianshu.com/p/56929416b4a1

The following link to the network disk is what I downloaded opencv package , The download link in the above article link is too slow

link ：https://pan.baidu.com/s/1o-uu54EwxZBFocR2he4BHg 
Extraction code ：1111 

3. Errors occurred According to this Article modification

https://blog.csdn.net/simonforfuture/article/details/101716181

The solution to the error in the above link Need some supplementary documents , See the link below

link ：https://pan.baidu.com/s/1M5QB_8vHT5nRJE3wJlL1Zg 
Extraction code ：1111 
 

attach ： If the network disk fails , Comment contact