问题描述：

输入文件比较大，所以采取了分块处理df = pd.read_csv(args.input,sep=',',iterator=True)

loop = True

chunkSize = 900000

while loop:

    try:

        chunk = df.get_chunk(chunkSize)

        chunk = chunk[ ~ chunk['Chr'].str.contains('_')]

        chunk_1 = sample_threshold(chunk,SampleThreshold)

        chunk_2 = depth_caculate(chunk_1,DepThreshold)

        chunk_3 = wilcoxon_test(chunk_2,SampleNum)

        print('already handled one chunk!')

        print('============================')

    except StopIteration:

        loop = False

        print("Iteration is stopped.")

请问一下我怎么才能在每一块处理好之后就写入文件，并且不会覆盖前面的？

问题解析：

df.to_csv(date+'.csv',index = False,header=0,mode='a')

关键是 mode参数