0

我有这个数据：

inventory = { HAMMER: (10,100),
              SCREW: (1, 1000),
              NAIL: (1, 1000),
              SCREWDRIVER: (8, 100),
              DRILL: (50, 20),
              WORKBENCH: (150, 5),
              HANDSAW: (15, 50),
              CHAINSAW: (80, 30)
            }

我写了以下函数：

def get_items(cheapness):
    """ Return a list of (item, (price, count)) tuples that are the given
    cheapness. Note that the second element of the tuple is another tuple. """

    if cheapness == 'CHEAP':
        return [(key, value) for (key,value) in inventory.items() if value in ((cost,quantity) for (cost, quantity) in inventory.values() if cost < 20)]
    elif cheapness == 'MODERATE':
        return [(key, value) for (key,value) in inventory.items() if value in ((cost,quantity) for (cost, quantity) in inventory.values() if 20 < cost < 100)]
    elif cheapness == 'EXPENSIVE':
        return [(key, value) for (key,value) in inventory.items() if value in ((cost,quantity) for (cost, quantity) in inventory.values() if cost > 100)]

我的问题是当我做 a 时print type(get_items(CHEAP))，我得到了<type 'NoneType'>. 如何将结果作为列表返回？

4

3 回答 3

5

此代码功能更强大，可能更易于维护：

def get_items(cheapness):
    def a(value):
        if cheapness == 'CHEAP':
            return value < 20
        if cheapness == 'MODERATE':
            return value >= 20 and value < 100
        if cheapness == 'EXPENSIVE':
            return value >= 100
        return False
    return filter(lambda x: a(x[1][0]), inventory.items())
于 2011-02-04T02:45:10.647 回答
3

说出你的意思：

def get_items(cheapness):
    """ Return a list of (item, (price, count)) tuples that are the given
    cheapness. Note that the second element of the tuple is another tuple. """

    if cheapness == 'CHEAP':
        return [(item, (price,count)) for (item, (price,count)) in inventory.items() if price < 20]
    elif cheapness == 'MODERATE':
        return [(item, (price,count)) for (item, (price,count)) in inventory.items() if price > 20 and price < 100]
    elif cheapness == 'EXPENSIVE':
        return [(item, (price,count)) for (item, (price,count)) in inventory.items() if price > 100]
于 2011-02-04T02:34:40.950 回答
1

打印类型（get_items（'CHEAP'））呢？（注意引号）

于 2011-02-04T02:36:21.060 回答