Windows 10， Python 3.8

pip install opencv-python

Could not fetch URL https://pypi.org/simple/pip/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/pip/ (Caused by SSLError("Can't connect to HTTPS URL because the SSL module is not available."))

解決辦法
 
前往下面地址，下載和安裝OpenSSL：
    https://slproweb.com/products/Win32OpenSSL.html

下載對應自己系統的OpenSSL的EXE安裝包，選擇的是 Win64 OpenSSL v1.1.1n （下載檔案連結  https://slproweb.com/download/Win64OpenSSL-1_1_1n.exe ），安裝之後就可以正常使用了（安裝在預設路徑C盤）。採用迅雷下載比較快。

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安裝 cv2

E:\Eprogramfiles\Anaconda3\Scripts>python
Python 3.8.10 (tags/v3.8.10:3d8993a, May  3 2021, 11:48:03) [MSC v.1928 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> exit()

E:\Eprogramfiles\Anaconda3\Scripts>pip install opencv-python -i https://pypi.mirrors.ustc.edu.cn/simple/