paython问题，修改增添代码将index强制转化为string

将index强制转化为string增加代码

f=open('train_list.txt','w')
path = "foods"
index = 0
for dirname in os.listdir(path):
    for fname in os.listdir(path+"/"+dirname):
        f.write(path+"/"+dirname+"/"+fname+"\t"+   +"\n")
    index = index+1
f.close()

f = open('train_list.txt', 'w')
    path = "foods"
    index = 0
    for dirname in os.listdir(path):
        for fname in os.listdir(path + "/" + dirname):
            f.write(path + "/" + dirname + "/" + fname + "\t" + +"\n")
        index = index + 1
    str(index)
    f.close()