三种打不开的文件

下面的 load 分别处理：路径不存在、内容是空的、缺少必要的列。运行程序看三次调用各交回什么码：

import csv, io

NEED = {"date", "store", "item", "qty", "price"}

def load(text):
    if text is None:
        return 4
    rows = list(csv.DictReader(io.StringIO(text)))
    if not rows:
        return 5
    if not NEED <= set(rows[0]):
        return 6
    return 0

cases = (None, "", "date,store\n2026-09-01,东门\n")
print("".join(str(load(c)) for c in cases))