win10 安装python、opencv、numpy遇到的问题

正常安装流程

1. 安装最新版本的python，我的是Python3.9.0，官网下载安装即可
2. 安装 opencv ，cmd.exe进入python的安装目录，进入目录Programs\Python\Python39\Lib\site-packages，cmd要管理员权限，安装命令
   pip install opencv-python
   非常顺利
3. 安装numpy
   pip install numpy
   安装成功

测试：python进入命令行
import cv2
import numpy
出错
The current Numpy installation () fails to pass a sanity check due to a bug in the windows runtime

1. 好吧，听说安装windows运行时程序管用，装了一个重启
   下载地址
   https://dl1.qwp365.cn/luo/3DMAGME-vcredist2015_x64.zip
   这个不知道管不管用，但是还是出错

2. 按照提示，找到了官网，开发团队有回答如下
   https://developercommunity.visualstudio.com/content/problem/1207405/fmod-after-an-update-to-windows-2004-is-causing-a.html
   下面是管用的一句话
   As a workaround, you temporarily pin to NumPy 1.19.3 (pip install numpy==1.19.3) which has a fixed version of OpenBLAS that works correctly in Windows 2004/20H2. This fix broken other things (Linux, Windows-on-docker) and so could not be retained in NumPy 1.19.4.
   大概就是降级到numpy1.19.3
   好的，执行
   首先卸载numpy1.19.4
   pip uninstall numpy
   pip install numpy==1.19.3
   再进入python命令行
   import cv2
   import numpy
   一切ok了

D:\Users\xxx\AppData\Local\Programs\Python\Python39\Lib\site-packages>python
Python 3.9.0 (tags/v3.9.0:9cf6752, Oct  5 2020, 15:34:40) [MSC v.1927 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import numpy
>>> import cv2
>>>