Operate values within a list of lists Python-CodePudding

I seek operating a list of lists as follows:

#          key
example = [[2,   2, -10, 'Yes'],
           [2,   8,  21, 'Yes'],
           [2,  19,  14, 'Non'],
           [2,  30, -22, 'Non'],
           [4, -15,  31, 'Yes'],
           [4,   2,  17, 'Yes'],
           [4,   3, -90, 'Non']]


# What I have tried through dictionaries 
dictsum = dict()
for i in example:
    if i[0] in dictsum.keys():
        if i[3] == "Yes":
            dictsum[i[0]][0] = dictsum[i[0]][0] i[1]
            dictsum[i[0]][1] = dictsum[i[0]][1] i[2]
    else:
        dictsum[i[0]] = [i[1], i[2]]
        
onlysum = [[k,v[0], v[1]] for k,v in dictsum.items()]

As noted, all rows 'i[1]' and 'i[2]' have been added, respecting their key 'i[0]' and a conditional 'i[3]'.

What I try to do is find the value furthest from zero if i[3] == "Non" and add that value respecting its corresponding key 'i[0]'

Something should be like this:

result = [[2,   10   30,   11  (-22)], 
          [4,   -13   3,   48  (-90)]]

# Finally
result = [[2, 40, -11], 
          [4, -10, -42]]

I clarify that this is an example raised by myself to understand how the lists are operated in these cases, I am not an expert. If someone knows a way to give you a solution and feedback, I appreciate that you share it, cordial greetings.

CodePudding user response：

You can do it like this:

dictsum = collections.defaultdict(lambda: [0, 0])
max_non_values = collections.defaultdict(lambda: [0, 0])

def special_max(x, y):
    if abs(x) < abs(y):
        return y
    elif abs(x) > abs(y):
        return x
    else:
        return max(x, y)


for key, val_1, val_2, include in example:
    if include == "Yes":
        dictsum[key][0] = dictsum[key][0]   val_1
        dictsum[key][1] = dictsum[key][1]   val_2
    else:
        max_non_values[key][0] = special_max(max_non_values[key][0], val_1)
        max_non_values[key][1] = special_max(max_non_values[key][1], val_2)

onlysum = [[k, dictsum[k][0] max_non_values[k][0], dictsum[k][1] max_non_values[k][1]] for k in dictsum]

Since you're taking a sum, using a defaultdict is faster and simpler than checking for the key in the dict; you also either need to make two passes, or use two dicts. Also, I would recommend making the values in "example" either a class, or at the very least a namedtuple. Collecting data as a heterogeneous list of unstructured integers and strings becomes unmanageable beyond a few lines of code.

CodePudding user response：

First collect the sums for all the "Yes" values:

dictsum = {i[0]: [sum(x[1] for x in example if x[0]==i[0] and x[-1]=="Yes"), 
                  sum(x[2] for x in example if x[0]==i[0] and x[-1]=="Yes")] for i in example}
>>> dictsum
{2: [10, 11], 4: [-13, 48]}

Update the 0th and 1st list elements for each key using max with the required key function:

output = {k: [v[0] max([l[1] for l in example if l[0]==k and l[-1]=="Non"], key=abs), \
              v[1] max([l[2] for l in example if l[0]==k and l[-1]=="Non"], key=abs)] \
          for k,v in dictsum.items()}

>>> output
{2: [40, -11], 4: [-10, -42]}