python - aggregate data in nested list structure

Question

I have a list with nested sub-list with the following structure

in_data = 
 [
   [
     ['name', 'name_1'],  
     ['item_B', '2'], 
     ['item_C', '3'], 
     ['item_D', '4']
   ],
   [
     ['name', 'name_2'], 
     ['item_B', '5'], 
     ['item_A', '2']
   ],
   [
     ['name', 'name_3'], 
     ['item_B', '6'], 
     ['item_C', '7']
   ]
]

I am trying to collect all data in in_data and make a unique list that contains sub-lists, one for all the "headers"/ names and one for each item + values in the correct order. So the information is preserved but in a different data-structure.

I want to achieve this list:

res_list = 
[
  ['name', ' name_1', ' name_2', 'name_3'], 
  ['item_B', '2', '5', '6'], 
  ['item_C', '3','-', '7'], 
  ['item_D', '4','-', '-'], 
  ['item_A', '-','2', '-'] 
]

I am trying to do it in the most pythonic way. I tried with for loops and also map() + lambda but no succeess.

would be the easy way?

. I tried with for loops and also map() + lambda - you need to post those attempts — RomanPerekhrest
– RomanPerekhrest, Commented Nov 10, 2019 at 16:03
What's with the name vs. Skill elements? The most Pythonic way would probably be using list comprehensions. — CristiFati
– CristiFati, Commented Nov 10, 2019 at 16:16
i'd recommend rethinking this structure. dictionaries seem to make much more sense here. — Paritosh Singh
– Paritosh Singh, Commented Nov 10, 2019 at 16:24

RomanPerekhrest · Accepted Answer · 2019-11-10 17:16:16Z

2

The optimized approach (powered by composite dict keys (<skill name>, <column name>) and dict.get method):

header = ['names']
names = set()
d = {}

for lst in in_data:
    col_name = lst[0][-1]
    header.append(col_name)
    for name, val in lst[1:]:
        names.add(name)
        d[name, col_name] = val

res = [[n, *[d.get((n, h), '-') for h in header[1:]]] for n in names]
res.insert(0, header)
print(res)

The output:

[['names', 'name_1', 'name_2', 'name_3'],
 ['item_C', '3', '-', '7'],
 ['item_D', '4', '-', '-'],
 ['item_B', '2', '5', '6'],
 ['item_A', '-', '2', '-']]

edited Nov 10, 2019 at 17:16

answered Nov 10, 2019 at 17:10

RomanPerekhrest

93.1k4 gold badges75 silver badges112 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

RomanPerekhrest Over a year ago

@PM2Ring, that's Ok

Ajax1234 · Accepted Answer · 2019-11-10 16:24:52Z

You can use collections.defaultdict:

import collections
in_data = [[['name', 'name_1'], ['item_B', '2'], ['item_C', '3'], ['item_D', '4']], [['Skill', 'name_2'], ['item_B', '5'], ['item_A', '2']], [['Skill', 'name_3'], ['item_B', '6'], ['item_C', '7']]]
d = [list(zip(['name', *b[0][1:]], i)) for b in in_data for i in b[1:]]
new_d = collections.defaultdict(dict)
for i in d:
   new_d[dict(i)['name']][i[-1][0]] = i[-1][-1]

all_names = list({i for b in new_d.values() for i in b})[::-1]
result = [['name', *all_names], *[[a, *[b.get(k, '-') for k in all_names]] for a, b in new_d.items()]]

Output:

[['name', 'name_1', 'name_2', 'name_3'], 
 ['item_B', '2', '5', '6'], 
 ['item_C', '3', '-', '7'], 
 ['item_D', '4', '-', '-'], 
 ['item_A', '-', '2', '-']]

Collectives™ on Stack Overflow

python - aggregate data in nested list structure

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related