How to compare 2 lists with each other in Python?

Question

I have the following 2 lists.

my_values = ['0,78', '0,40', '0,67']

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']]

Now for every lists in my_list I want to check at what index[2] is index[3] equal to a value in my_values. index[2] is the 3th row in my_list and index[4] is the 4th row in my_list So short said:

1. For Morocco I want to check at what index[2] is index[3] == 0,78
2. For Spain I want to check at what index[2] is index[3] == 0,40
3. For Italy I want to check at what index[2] is index[3] == 0,67

This is the code I tried:

my_answers = []
for key,sublists in itertools.groupby(my_list,lambda y:y[0]): 
    v = min(x for x in sublists if float(x[3].replace(',', '.')) == x for x in my_values); 
    my_answers.append(v[-2])
    
print(my_answers)

This is what I receive:

ValueError: min() arg is an empty sequence

This is what I expected:

188,49
189,01
188,61

Answer 1

Is this what you want?

my_values = ['0,78', '0,40', '0,67']

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'],
]

print("\n".join(i[2] for i in my_list if i[3] in my_values))

Output:

188,49
189,01
188,61

Here's what the one-liner does:

• loops over the lists in your my_list and checks the value from each sub-list with the index [3] againts the my_value list
• if the condition is True, it "keeps" the value from index [2]
• finally it joins all the values that matched the above e.g. 189,01
• By the way, the i[2] for i in my_list if i[3] in my_values is a generator
• "\n" is a new line character

EDIT:

If you want the output to be in a list, just do this:

yet_another_list = [i[2] for i in my_list if i[3] in my_values]
print(yet_another_list)

This gives you:

['188,49', '189,01', '188,61']