根据安装步骤:
pip install PyQt5 -i https://pypi.douban.com/simple
pip install PyQt5-tools -i https://pypi.douban.com/simple
但是在以下路径都找不到designer.exe
C:\Users\15259\AppData\Roaming\Python\Python39\site-packages\pyqt5_tools
在Scripts下找到了文件(直接在Python39中搜索文件找到的。。。)
C:\Users\15259\AppData\Roaming\Python\Python39\site-packages\qt5_applications\Qt\bin