请写一个python sift特征匹配算法

好的，以下是基于OpenCV库实现的SIFT特征匹配算法的Python代码：

import cv2

# 读取待匹配图像和匹配参考图像
img1 = cv2.imread('img1.jpg', cv2.IMREAD_GRAYSCALE)
img2 = cv2.imread('img2.jpg', cv2.IMREAD_GRAYSCALE)

# 创建SIFT对象并检测关键点及特征描述符
sift = cv2.xfeatures2d.SIFT_create()
keypoints1, descriptors1 = sift.detectAndCompute(img1, None)
keypoints2, descriptors2 = sift.detectAndCompute(img2, None)

# 创建暴力匹配器并匹配特征描述符
bf = cv2.BFMatcher()
matches = bf.match(descriptors1, descriptors2)

# 将匹配结果按照特征点间距离由小到大排序
matches = sorted(matches, key=lambda x: x.distance)

# 取出前10个最佳匹配结果并可视化
img3 = cv2.drawMatches(img1, keypoints1, img2, keypoints2, matches[:10], None, flags=cv2.DrawMatchesFlags_NOT_DRAW_SINGLE_POINTS)
cv2.imshow("SIFT matches", img3)
cv2.waitKey(0)
cv2.destroyAllWindows()