readline正在读取多行

Question

因此代码非常简单，如果用户没有输入可行的文件，那么程序会关闭，但是当我试图将打开的文件从open_file（）函数移动到main时函数，然后在read_file（）函数中使用它。然而，当我打印它来测试它时，它打印的不仅仅是第一行......我只是试图抓住第二行用逗号分隔的第四个单词。

#opens the file for data
def open_file():
    input_file = input("Enter a food crop file: ")
    try: 
        f1 = open(input_file,"r")
        next(f1)
    except FileNotFoundError:
        print("File not found; terminating program.")
        return False,False
    input_file2 = input("Enter a non-food crop file: ")
    try:
        f2 = open(input_file2,"r")
        next(f2)
    except FileNotFoundError:
        print("File not found; terminating program.")

        return False,False
    return f1,f2
def read_files(f1,f2):
    line1 = f1.readline()
    list_line1 = line1.replace(',','').split()
    product1 = list_line1[3]
    line2 = f2.readline()
    list_line2 = line2.replace(',','').split()
    product2 = list_line2[3]
    print(product1,product2)
    return product1,product2

#main fucntion, will call all other functions  
def main():
    f1,f2 = open_food_file()
    while f1 != False:


        product1,product2 = read_files(f1,f2)

#launches code
main()

看起来应该是这样的

Enter a food crop file: file_name.csv

Enter a non-food crop file: file_name.csv
product1 = 4th item in list for file1 here
product2 = 4th item in list for file2 here

它返回此信息，但随后

出错

File "C:/COLLEGE/CSE/CSE 231/Code/redo.py", line 28, in read_files
    product1 = list_line1[3]

IndexError: list index out of range