UnboundLocalError：本地变量python

我是python新手，在尝试运行下面的代码时，一直出现上面的错误。有谁能帮忙或提供指导吗，谢谢:)

def feature_4():
    flower_update = input("Enter the name of the flower you wish to change the price:"
                          "Lily, Rose, Tulip, Iris, Daisy, Orchid, Dahlia, Peony")
    flower_new_price = input("Enter the updated price of the flower")
    with open('flowers.txt') as amend_price:

        for line in amend_price:
            flower_price = int(line.split(',')[1])
            flower_name = str(line.split(',')[0])

    if flower_name == flower_update:
        flower_price.append(flower_new_price)
    print("The new price of", flower_update, "is", flower_new_price) 

解决方案：

你碰到了一个常见的问题，你不能同时读取一个文件和修改它.至少我不知道如何做到这一点，你可以使用几个选项来实现你的目标。

当用 “w “标志写的时候，你会擦掉现有的文件，因此你要先读取内存中的文件，修改它，把它的数据保留在内存或临时文件中，然后重写它。

我将跳过临时文件。

def feature_4(flower_file='flowers.txt'):

    flower_update = input("Enter the name of the flower you wish to change the price:"
                          "Lily, Rose, Tulip, Iris, Daisy, Orchid, Dahlia, Peony")
    flower_new_price = input("Enter the updated price of the flower")
    # here you should check that the input matches what you are expecting

    flower, price = [], []
    with open(flower_file) as amend_price:

        for line in amend_price:
            spt = line.strip().split(",")
            flower_price = int(spt[1])
            flower_name = str(spt[0])

            if flower_name == flower_update :
                price.append(flower_new_price)

            else:
                price.append(flower_price)

            flower.append(flower_name)

    with open(flower_file, "w") as f_:
        for i, v in enumerate(flower):
            f_.write("{},{}\n".format(v, str(price[i])))

    print("The new price of", flower_update, "is", flower_new_price)