ModuleNotFoundError: No module named ‘dateutil’但是pip install却提示已经安装解决办法

问题描述: 运行一段程序的时候会提示: Traceback (most recent call last): File "sigmoid.py", line 3, in import matplotlib.pylab as plt File "D:\software\python\python37\lib\site-packages\matplotlib\__init__.py", line 205, in _check_versions() File "D:\software\python\python37\lib\site-packages\matplotlib