Question

I have a django queryset that returns a list of values:

[(client pk, timestamp, value, task pk), (client pk, timestamp, value, task pk),....,].

I am trying to get it to return a dictionary of this format:

{client pk:[[timestamp, value],[timestamp, value],...,], client pk:[list of lists],...,}

The values_list may have multiple records for each client pk. I have been able to get dictionaries of lists for client or task pk using:

def dict_from_vl(vls_list):
    keys=[values_list[x][3] for x in range(0,len(values_list),1)]
    values = [[values_list[x][1], values_list[x][2]] for x in range(0,len(values_list),1)]
    target_dict=dict(zip(keys,values))
    return target_dict

However using this method, values for the same key write over previous values as it iterates through the values_list, rather than append them to a list. So this works great for getting the most recent if the values list is sorted oldest records to newest, but not for the purpose of creating a list of lists for the dict value.

Answer 1

Instead of target_dict=dict(zip(keys,values)), do

target_dict = defaultdict(list)
for i, key in enumerate(keys):
    target_dict[k].append(values[i])

(defaultdict is available in the standard module collections.)