python3 简单实现从csv文件中读取内容，并对内容进行分类统计

新手python刚刚上路，在实际工作中遇到如题所示的问题，尝试使用python3简单实现如下，欢迎高手前来优化
 
import csv
 
#打开文件，用with打开可以不用去特意关闭file了，python3不支持file()打开文件，只能用open()
with open("dk0519_1.csv","r",encoding="utf-8") as csv_file:
     #读取csv文件，返回的是迭代类型
    read = csv.reader(csv_file)
    alist = []
    bdict = []
    cdict = []
    tmp = []
    for i in read:
        alist.append(i[0].split("\t"))
    for a in alist[1:]:
        print(a)
        bdict.append((a[0].split("?")[0],a[1]))
    for b in bdict:
        num = int(b[1])
        j = bdict.index(b) + 1
        while j <= (len(bdict)-1) :
            if b[0] not in tmp:
                if b[0] == bdict[j][0]:
                    num += int(bdict[j][1])
                    j += 1
                else:
                    j +=1
            else:
                j +=1
        if b[0] not in tmp:
            cdict.append((b[0],num))
        else:
            pass
        tmp.append(b[0])
 
with open('re_dk0519_1.csv','w',encoding="utf-8") as write_csvfile:
    writer = csv.writer(write_csvfile)
    writer.writerows(cdict)