如何根据 Python 中的多个其他列表过滤列表？答案

【问题标题】：How to filter a list based on multiple other lists in Python?如何根据 Python 中的多个其他列表过滤列表？
【发布时间】：2021-04-05 04:12:25
【问题描述】：

我有 3 个列表：

minimal_values = ['0,32', '0,35', '0,45']
maximal_values = ['0,78', '0,85', '0,72']

my_list = [
    ['Morocco', 'Meat', '190,00', '0,15'], 
    ['Morocco', 'Meat', '189,90', '0,32'], 
    ['Morocco', 'Meat', '189,38', '0,44'],
    ['Morocco', 'Meat', '188,94', '0,60'],
    ['Morocco', 'Meat', '188,49', '0,78'],
    ['Morocco', 'Meat', '187,99', '0,101'],
    ['Spain', 'Meat', '190,76', '0,10'], 
    ['Spain', 'Meat', '190,16', '0,20'], 
    ['Spain', 'Meat', '189,56', '0,35'],
    ['Spain', 'Meat', '189,01', '0,40'],
    ['Spain', 'Meat', '188,13', '0,75'],
    ['Spain', 'Meat', '187,95', '0,85'],
    ['Italy', 'Meat', '190,20', '0,11'],
    ['Italy', 'Meat', '190,10', '0,31'], 
    ['Italy', 'Meat', '189,32', '0,45'],
    ['Italy', 'Meat', '188,61', '0,67'],
    ['Italy', 'Meat', '188,01', '0,72'],
    ['Italy', 'Meat', '187,36', '0,80']]

我想根据index [-1] 以及minimal_values 和maximal_values 中的值过滤my_list。像这样：

对于摩洛哥，我只想要index[-1] 在0,32 和0,78 之间的行
对于西班牙，我只想要index[-1] 在0,35 和0,85 之间的行
对于意大利，我只想要index[-1] 在0,45 和0,72 之间的行

我最终希望my_list 看起来像这样：

my_list = [
    ['Morocco', 'Meat', '189,90', '0,32'], 
    ['Morocco', 'Meat', '189,38', '0,44'],
    ['Morocco', 'Meat', '188,94', '0,60'],
    ['Morocco', 'Meat', '188,49', '0,78'],
    ['Spain', 'Meat', '189,56', '0,35'],
    ['Spain', 'Meat', '189,01', '0,40'],
    ['Spain', 'Meat', '188,13', '0,75'],
    ['Spain', 'Meat', '187,95', '0,85'],
    ['Italy', 'Meat', '189,32', '0,45'],
    ['Italy', 'Meat', '188,61', '0,67'],
    ['Italy', 'Meat', '188,01', '0,72']]

这是我试过的代码：

for l in my_list:
    if l[-1] >= [x for x in minimal_values] and <= [x for x in maximal_values]:
        print(l)

我收到以下输出：

SyntaxError: invalid syntax

【问题讨论】：

逗号不是你想象的那样，字符串也不是你可以用那种方式比较的。您应该将所有字符串数字转换为浮点数。如果你的列表很长，你也应该使用pandas。
我对@987654340@ 的值感到困惑。那应该代表0.101 还是不同的东西？如果0.101 似乎不符合其他值的模式

标签： python list for-loop if-statement indexing

【解决方案1】：

你可以这样做：

minimal_values = ['0,32', '0,35', '0,45']
maximal_values = ['0,78', '0,85', '0,72']

my_list = [
    ['Morocco', 'Meat', '190,00', '0,15'], 
    ['Morocco', 'Meat', '189,90', '0,32'], 
    ['Morocco', 'Meat', '189,38', '0,44'],
    ['Morocco', 'Meat', '188,94', '0,60'],
    ['Morocco', 'Meat', '188,49', '0,78'],
    ['Morocco', 'Meat', '187,99', '0,101'],
    ['Spain', 'Meat', '190,76', '0,10'], 
    ['Spain', 'Meat', '190,16', '0,20'], 
    ['Spain', 'Meat', '189,56', '0,35'],
    ['Spain', 'Meat', '189,01', '0,40'],
    ['Spain', 'Meat', '188,13', '0,75'],
    ['Spain', 'Meat', '187,95', '0,85'],
    ['Italy', 'Meat', '190,20', '0,11'],
    ['Italy', 'Meat', '190,10', '0,31'], 
    ['Italy', 'Meat', '189,32', '0,45'],
    ['Italy', 'Meat', '188,61', '0,67'],
    ['Italy', 'Meat', '188,01', '0,72'],
    ['Italy', 'Meat', '187,36', '0,80']]
    

# Convert values to float.
minimal_values = [float(i.replace(',', '.')) for i in minimal_values]
maximal_values = [float(i.replace(',', '.')) for i in maximal_values]

# Collect all unique countries in a list.
countries = list(set(country[0] for country in my_list))

results = []
for l in my_list:
    i = countries.index(l[0])
    if minimal_values[i] <= float(l[-1].replace(',', '.')) <= maximal_values[i]:
        results.append(l)
 print(results)

输出：

[['Morocco', 'Meat', '189,90', '0,32'],
['Morocco', 'Meat', '189,38', '0,44'],
['Morocco', 'Meat', '188,94', '0,60'],
['Morocco', 'Meat', '188,49', '0,78'],
['Spain', 'Meat', '189,56', '0,35'],
['Spain', 'Meat', '189,01', '0,40'],
['Spain', 'Meat', '188,13', '0,75'],
['Spain', 'Meat', '187,95', '0,85'],
['Italy', 'Meat', '189,32', '0,45'],
['Italy', 'Meat', '188,61', '0,67'],
['Italy', 'Meat', '188,01', '0,72']]

【讨论】：

【解决方案2】：

您最好先将国家/地区名称放在单独的列表中。见下文：

countries=[]
for i in my_list:
    if i[0] not in countries:
        countries.append(i[0])

#['Morocco', 'Spain', 'Italy']

现在将每个国家/地区的最小值和最大值保存在字典中：

d={countries[i]:(float(minimal_values[i].replace(',','.')), float(maximal_values[i].replace(',','.'))) for i in range(len(countries))}

#{'Morocco': (0.32, 0.78), 'Spain': (0.35, 0.85), 'Italy': (0.45, 0.72)}

现在进行过滤，如下所示：

result=[]

for i in my_list:
    if float(i[-1].replace(',','.'))>=d[i[0]][0] and float(i[-1].replace(',','.'))<=d[i[0]][1]:
        result.append(i)

完整代码和输出：

countries=[]
for i in my_list:
    if i[0] not in countries:
        countries.append(i[0])

d={countries[i]:(float(minimal_values[i].replace(',','.')), float(maximal_values[i].replace(',','.'))) for i in range(len(countries))}

result=[]

for i in my_list:
    if float(i[-1].replace(',','.'))>=d[i[0]][0] and float(i[-1].replace(',','.'))<=d[i[0]][1]:
        result.append(i) 

>>> print(result)

[['Morocco', 'Meat', '189,90', '0,32'], 
 ['Morocco', 'Meat', '189,38', '0,44'], 
 ['Morocco', 'Meat', '188,94', '0,60'], 
 ['Morocco', 'Meat', '188,49', '0,78'], 
 ['Spain', 'Meat', '189,56', '0,35'], 
 ['Spain', 'Meat', '189,01', '0,40'], 
 ['Spain', 'Meat', '188,13', '0,75'], 
 ['Spain', 'Meat', '187,95', '0,85'], 
 ['Italy', 'Meat', '189,32', '0,45'], 
 ['Italy', 'Meat', '188,61', '0,67'], 
 ['Italy', 'Meat', '188,01', '0,72']]

【讨论】：

【解决方案3】：

首先，您需要在每次将其与其他物品进行比较时提及该物品。如果您想通过将它们与最小值和最大值进行比较来对它们进行排序，那么最好为新值创建一个新列表。

minimal_values = ['0,32', '0,35', '0,45']
maximal_values = ['0,78', '0,85', '0,72']

my_list = [
    ['Morocco', 'Meat', '190,00', '0,15'],
    ['Morocco', 'Meat', '189,90', '0,32'],
    ['Morocco', 'Meat', '189,38', '0,44'],
    ['Morocco', 'Meat', '188,94', '0,60'],
    ['Morocco', 'Meat', '188,49', '0,78'],
    ['Morocco', 'Meat', '187,99', '0,101'],
    ['Spain', 'Meat', '190,76', '0,10'],
    ['Spain', 'Meat', '190,16', '0,20'],
    ['Spain', 'Meat', '189,56', '0,35'],
    ['Spain', 'Meat', '189,01', '0,40'],
    ['Spain', 'Meat', '188,13', '0,75'],
    ['Spain', 'Meat', '187,95', '0,85'],
    ['Italy', 'Meat', '190,20', '0,11'],
    ['Italy', 'Meat', '190,10', '0,31'],
    ['Italy', 'Meat', '189,32', '0,45'],
    ['Italy', 'Meat', '188,61', '0,67'],
    ['Italy', 'Meat', '188,01', '0,72'],
    ['Italy', 'Meat', '187,36', '0,80']]

my_list2 = []
for country in my_list:
    if country[0] == "Morocco" and country[-1] >= minimal_values[0] and country[-1] <= maximal_values[0]:
        my_list2.append(country)

    if country[0] == "Spain" and country[-1] >= minimal_values[1] and country[-1] <= maximal_values[1]:
        my_list2.append(country)

    if country[0] == "Italy" and country[-1] >= minimal_values[2] and country[-1] <= maximal_values[2]:
        my_list2.append(country)

print(my_list2)

如您所见，每次我想比较它们时，我都提到了每个列表的最后一个值，该值的索引为 -1。可以比较字符串，但如果下次将值设置为浮点数或整数会更好。这将使过程更容易。

你会得到的输出是：

['Morocco', 'Meat', '189,90', '0,32'], 
    ['Morocco', 'Meat', '189,38', '0,44'],
    ['Morocco', 'Meat', '188,94', '0,60'],
    ['Morocco', 'Meat', '188,49', '0,78'],
    ['Spain', 'Meat', '189,56', '0,35'],
    ['Spain', 'Meat', '189,01', '0,40'],
    ['Spain', 'Meat', '188,13', '0,75'],
    ['Spain', 'Meat', '187,95', '0,85'],
    ['Italy', 'Meat', '189,32', '0,45'],
    ['Italy', 'Meat', '188,61', '0,67'],
    ['Italy', 'Meat', '188,01', '0,72']]

【讨论】：