如何向列表添加值？

Question

我有以下列表。

导入日期时间

my_list = [
    ['Morocco', 'Fish', datetime.datetime(2020, 11, 17, 0, 0),'0,012'], 
    ['Morocco', 'Fish', datetime.datetime(2020, 11, 17, 0, 0),'0,153'], 
    ['Morocco', 'Fish', datetime.datetime(2020, 11, 17, 0, 0), '0,114'],
    ['Morocco', 'Fish', datetime.datetime(2020, 11, 17, 0, 0), '0,109'],
    ['Morocco', 'Fish', datetime.datetime(2020, 11, 17, 0, 0), '0,252'],
    ['Spain', 'Fish', datetime.datetime(2020, 11, 17, 0, 0), '0,012'], 
    ['Spain', 'Fish', datetime.datetime(2020, 11, 17, 0, 0), '0,113'], 
    ['Spain', 'Fish', datetime.datetime(2020, 11, 17, 0, 0), '0,116'],
    ['Spain', 'Fish', datetime.datetime(2020, 11, 17, 0, 0), '0,250'],
    ['Spain', 'Fish', datetime.datetime(2020, 11, 17, 0, 0), '0,266']]

使用下面的代码，我获取了每个国家/地区的最高值。然而，这是正确的。我还想将国家添加到 max_price_per_list

max_prices_by_country = {}
for item in my_list:
    price = max_prices_by_country.setdefault(item[0], 0)
    max_prices_by_country[item[0]] = max(price, float(item[-1].replace(',', '.')))
    country = item[0]

max_price_per_list = [[country] + [str(price).replace('.', ',') for price in max_prices_by_country.values()]]

print(max_price_per_list)

这是我当前的输出：

[['Spain', '0,252', '0,266']]

这是我的首选输出：

[[Morocco, '0,252'], 
['Spain', '0,266']]

Answer 1

也许你可以这样做

import datetime
my_list = [
    ['Morocco', 'Fish', datetime.datetime(2020, 11, 17, 0, 0),'0,012'], 
    ['Morocco', 'Fish', datetime.datetime(2020, 11, 17, 0, 0),'0,153'], 
    ['Morocco', 'Fish', datetime.datetime(2020, 11, 17, 0, 0), '0,114'],
    ['Morocco', 'Fish', datetime.datetime(2020, 11, 17, 0, 0), '0,109'],
    ['Morocco', 'Fish', datetime.datetime(2020, 11, 17, 0, 0), '0,252'],
    ['Spain', 'Fish', datetime.datetime(2020, 11, 17, 0, 0), '0,012'], 
    ['Spain', 'Fish', datetime.datetime(2020, 11, 17, 0, 0), '0,113'], 
    ['Spain', 'Fish', datetime.datetime(2020, 11, 17, 0, 0), '0,116'],
    ['Spain', 'Fish', datetime.datetime(2020, 11, 17, 0, 0), '0,250'],
    ['Spain', 'Fish', datetime.datetime(2020, 11, 17, 0, 0), '0,266']]
    
max_prices_by_country = {}
for item in my_list:
    country = item[0]

    # if country is not in dict add it with a value, 0
    if country not in max_prices_by_country:
        max_prices_by_country[country] = 0

    # get the max value of existing and incoming value (which is item[0])
    max_prices_by_country[country] = max(max_prices_by_country[country], float(item[-1].replace(',', '.')))

# convert the dict to a list of array.
max_price_per_list = [[k, str(max_prices_by_country[k]).replace('.', ',')] for k in max_prices_by_country]

print(max_price_per_list)

Answer 2

对于程序的最后一部分，您似乎在尝试将字典拼合成一个列表。

你可以做一些不会像这样的长命令：

max_price_per_list = list(max_prices_by_country.items())

如何向列表添加值？

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