python一段代码看不懂

雷欧库珀

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'''
这是某一个类中的一个函数，step2按照x1排序这一步看不懂
sorted(cleaned, key =operator.itemgetter(0))这个我知道是按照列表的第一维度也就是x1排序
sorted(cleaned, key =operator.itemgetter(1))这个我也知道是按照列表的第二维度也就是y1排序
sorted(cleaned, key =operator.itemgetter(0, 1))为什么这个还是按照x1排序呢?
'''
    def identify_blocks(self,image, lines, make_copy=True):
        if make_copy:
            new_image = np.copy(image)
        #Step 1: 过滤部分直线
        cleaned = []
        for line in lines:
            for x1,y1,x2,y2 in line:
                if abs(y2-y1) <=1 and abs(x2-x1) >=25 and abs(x2-x1) <= 55:
                    cleaned.append((x1,y1,x2,y2))
        
        #Step 2: 对直线按照x1进行排序
        import operator
        list1 = sorted(cleaned, key=operator.itemgetter(0, 1))
        
        #Step 3: 找到多个列，相当于每列是一排车
        clusters = {}
        dIndex = 0
        clus_dist = 10
    
        for i in range(len(list1) - 1):
            distance = abs(list1[i+1][0] - list1[i][0])
            if distance <= clus_dist:
                if not dIndex in clusters.keys(): clusters[dIndex] = []
                clusters[dIndex].append(list1[i])
                clusters[dIndex].append(list1[i + 1]) 
    
            else:
                dIndex += 1
        
        #Step 4: 得到坐标
        rects = {}
        i = 0
        for key in clusters:
            all_list = clusters[key]
            cleaned = list(set(all_list))
            if len(cleaned) > 5:
                cleaned = sorted(cleaned, key=lambda tup: tup[1])
                avg_y1 = cleaned[0][1]
                avg_y2 = cleaned[-1][1]
                avg_x1 = 0
                avg_x2 = 0
                for tup in cleaned:
                    avg_x1 += tup[0]
                    avg_x2 += tup[2]
                avg_x1 = avg_x1/len(cleaned)
                avg_x2 = avg_x2/len(cleaned)
                rects[i] = (avg_x1, avg_y1, avg_x2, avg_y2)
                i += 1
        
        print("Num Parking Lanes: ", len(rects))
        #Step 5: 把列矩形画出来
        buff = 7
        for key in rects:
            tup_topLeft = (int(rects[key][0] - buff), int(rects[key][1]))
            tup_botRight = (int(rects[key][2] + buff), int(rects[key][3]))
            cv2.rectangle(new_image, tup_topLeft,tup_botRight,(0,255,0),3)
        return new_image, rects

这是为什么呢？

JokerX

itemgetter(0, 1) 先按第 0 个排序，如果相等按第 1 个排序