Recently in learning flask web development, encountered such a problem, is according to the book on the code, run is an Internal server error, because halfway to learn for the sake of convenience, to switch to pycharm to develop, pycharm automatically help me to create a virtual environment, the book says the venv can I do not pollute the environment, but in fact I use, because the initial development on sublime does directly, cause I have a lot of local module, reoccupy pycharm, I changed the environment variable a lot, changed it all to venV, and then this error happened, you can try to delete VENV, use the native environment, and at the same time, change the environment variable back to the native, you can use it. Personal analysis, think should be two environments exist some kind of conflict.

Reproduced in: https://www.cnblogs.com/sgatbl/p/9134283.html