Python的行为我不明白

我正在为需要搜索数据库（csv）的产品的学校做一个项目。它通过将验证的EAN-8代码与每行的第0列进行匹配，并在for循环中进行扫描。有一个尝试，除了试图匹配代码，然后显示产品，除了它是否找不到它，当它打算打印“PRODUCT NOT FOUND，Try again”时。我尝试了不同的迭代，如果，否则，如果，elif结合尝试，除了但无济于事。请帮忙。Python的行为我不明白

#code is the barcode 
     for row in csv_file: 
      try: 
       if code == row[0]: 
        print("This product is: ", row[1], "\n", "Quantity left in stock: ", row[2], "\n", "Cost: ", row[3], "\n") 
        quant = int(input("How many do you you want?: ")) 
        if quant > int(row[2]): 
         print("We don't have that many, try again") 
         order() 
        else: 
         orderrow = row 
         orderrow[2] = quant 
         orderrow[3] = float(orderrow[3]) * quant 
         totalcost = totalcost + orderrow[3] 
         orderlist.append(orderrow) 


      except: 
       print("ITEM NOT FOUND, TRY AGAIN") 
       order()

来源

2016-04-14 fpv_rex

有什么例外，你期待'除了'要赶上？ – user2357112

很明显，你没有得到任何异常。我认为你误解了“尝试/除了”实际上做了什么。 –

正确的方法是在找到匹配的行时设置变量。循环完成后，检查变量以查看是否找到任何内容，如果没有，则打印该消息。

found = false 
for row in csv_file: 
    if code == row[0]: 
     found = true 
     print("This product is: ", row[1], "\n", "Quantity left in stock: ", row[2], "\n", "Cost: ", row[3], "\n") 
     quant = int(input("How many do you you want?: ")) 
     if quant > int(row[2]): 
      print("We don't have that many, try again") 
      order() 
     else: 
      orderrow = row 
      orderrow[2] = quant 
      orderrow[3] = float(orderrow[3]) * quant 
      totalcost = totalcost + orderrow[3] 
      orderlist.append(orderrow) 
if !found 
    print("ITEM NOT FOUND, TRY AGAIN") 
    order()

来源

2016-04-14 16:37:52 Barmar

感谢@Barmar这真的帮了大忙！ –

您需要合适的if-else而不是try-catch。这里没有Exception。如何：

for row in csv_file: 
    if code == row[0]: 
     print("This product is: ", row[1], "\n", "Quantity left in stock: ", row[2], "\n", "Cost: ", row[3], "\n") 
     quant = int(input("How many do you you want?: ")) 
     if quant > int(row[2]): 
      print("We don't have that many, try again") 
      order() 
     else: 
      orderrow = row 
      orderrow[2] = quant 
      orderrow[3] = float(orderrow[3]) * quant 
      totalcost = totalcost + orderrow[3] 
      orderlist.append(orderrow) 
    else: 
     print("ITEM NOT FOUND, TRY AGAIN") 
     order()

来源

2016-04-14 16:26:21 th3an0maly

这将为文件中没有匹配代码的每一行打印“ITEM NOT FOUND”。 – Barmar

@Barmar我没有验证OP的逻辑。只需修复不必要的'try-except'并指向'if-else'。看起来这是所有OP需要在这一点:) – th3an0maly

编辑我的评论。谢谢 – th3an0maly

Python的行为我不明白

回答

相关问题