[j for i in ann["segmentation"] for j in i]
今天遇到一个有意思的代码 [j for i in ann["segmentation"] for j in i]
不太常见,列表推导式里有两个 for
ann=dict()
ann["segmentation"] = [[1,2],[2,3]]
[j for i in ann["segmentation"] for j in i] # [1, 2, 2, 3]
其实效果相当于:
result = []
for i in ann["segmentation"]:
for j in i:
result.append(j)
展平列表了。