SIFT opencv-python 调用报错

（1）在调用sift = cv2.xfeatures2d.SIFT_create()

出现下面报错：

raceback (most recent call last):
  File "", line 1, in
cv2.error: OpenCV(4.0.1) ../opencv_contrib/modules/xfeatures2d/src/sift.cpp:1207: error: (-213:The function/feature is not implemented) This algorithm is patented and is excluded in this configuration; Set OPENCV_ENABLE_NONFREE CMake option and rebuild the library in function 'create'

（2）原因：sift算法的专利问题，部分opencv版本的Sift/Surf算法无法使用

（3）解决办法：

卸载当前opencv-python和opencv-contrib-python第三方包

conda list 命令查看是否有opencv-python和opencv-contrib-python：

pip install opencv-python==3.4.2.17

pip install opencv-contrib-python==3.4.2.17

安装完成：