When you download external packages, you would usually use the following commands in terminal: pip3 download <package>, e.g. pip3 download wxpython However default pip3 download source is from overseas. This leads to a very slow download speed -- 20kb/s for me. It took me half a day just to download the OpenCV4! Solution: Switch to a nearby server mirror. I can download packages at 2MbPS now! Shown below, the solution from https://www.jianshu.com/p/e993bdfff7b3 is clear. Thanks! [global] index-url = http://mirrors.aliyun.com/pypi/simple/ [install] trusted-host=mirrors.aliyun.com Fell free to comment below if you encountered any quesitions.