如何使用类在循环中合并多个数据帧

class DataFrameMerger:
    def __init__(self):
        self.merged_frame = None

    def merge_frames(self, frames):
        for frame in frames:
            if self.merged_frame is None:
                self.merged_frame = frame
            else:
                self.merged_frame = self.merged_frame.append(frame)

        return self.merged_frame

# 创建DataFrameMerger对象
merger = DataFrameMerger()

# 创建多个数据帧
frame1 = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]})
frame2 = pd.DataFrame({'A': [7, 8, 9], 'B': [10, 11, 12]})
frame3 = pd.DataFrame({'A': [13, 14, 15], 'B': [16, 17, 18]})

# 合并数据帧
merged_frame = merger.merge_frames([frame1, frame2, frame3])

# 打印合并后的数据帧
print(merged_frame)