Easy way to compare values within all dicts in list of dicts?-CodePudding

Let's say I have a list of dicts, called mydict, that looks like like this:

[{'id': 6384,
  'character': 'Thomas A. Anderson / Neo',
  'credit_id': '52fe425bc3a36847f80181c1',
  'movie_id': 603},
 {'id': 2975,
  'character': 'Morpheus',
  'credit_id': '52fe425bc3a36847f801818d',
  'movie_id': 603},
 {'id': 530,
  'character': 'Trinity',
  'credit_id': '52fe425bc3a36847f8018191',
  'movie_id': 603},
 {'id': 1331,
  'character': 'Agent Smith',
  'credit_id': '52fe425bc3a36847f8018195',
  'movie_id': 603},
 {'id': 3165802,
  'character': 'MP Sergeant #1',
  'credit_id': '62ade87f4142910051c8e002',
  'movie_id': 28},
 {'id': 18471,
  'character': 'Self',
  'credit_id': '6259ed263acd2016291eef43',
  'movie_id': 963164},
 {'id': 74611,
  'character': 'Self',
  'credit_id': '6259ed37ecaef515ff68cae6',
  'movie_id': 963164}]

and I want to get all pairs of mydict['id'] values that have the same mydict['movie_id'] value - using only Python standard libraries. Essentially, returning

(6384, 2975)
(6384, 530)
(6384, 1331)
....
(18471, 74611)

Looping through every possible combination seems possible, but slow, with something like this.

results=[]
for i in mydict:
    for j in mydict:
        current = i['movie_id'] 
        next = j['movie_id']
    if current==next:
        results.append(i['id'], j['id'])

Is there a dictionary comprehension way to achieve the same result?

CodePudding user response：

Consider using a collections.defaultdict() to group by movie_id. Then use itertools.combinations() to loop over them pairwise:

from collections import defaultdict
from itertools import combinations

d = defaultdict(list)
for movie in credits:
    d[movie['movie_id']].append(movie['id'])

for group in d.values():
    for pair in combinations(group, 2):
        print(pair)

For the given dataset, this outputs:

(6384, 2975)
(6384, 530)
(6384, 1331)
(2975, 530)
(2975, 1331)
(530, 1331)
(18471, 74611)

CodePudding user response：

An easy and understandable solution is to use the pandas library to do so.

import pandas as pd
my_data = mydict
df = pd.DataFrame.from_dict(my_data)
print(
    df[ df['id'] == df['movie_id'] ]
    )

This should work ok.

CodePudding user response：

You can do with groupby and combinations,

While using the groupby it's expected the similar movie_id appear together in main list, If not you have to sort the main list with movie_id.

In [18]: from itertools import groupby

In [19]: from itertools import combinations

In [20]: for k,l in groupby(mydict, key=lambda x:x['movie_id']):
    ...:     print(list(combinations([i.get('id') for i in l], 2)))
    ...: 
[(6384, 2975), (6384, 530), (6384, 1331), (2975, 530), (2975, 1331), (530, 1331)]
[]
[(18471, 74611)]

CodePudding user response：

Using pandas:

#lst is your list of dicts
out = pd.DataFrame(lst).groupby('movie_id')['id'].apply(
    lambda x: list(itertools.combinations(x, 2))).to_dict()

Using itertools:

out = {
        k: list(combinations([d['id'] for d in list(g)], 2))
        for k, g in groupby(lst, lambda x: x['movie_id'])
      }

print(out):

{28: [],
 603: [(6384, 2975),
  (6384, 530),
  (6384, 1331),
  (2975, 530),
  (2975, 1331),
  (530, 1331)],
 963164: [(18471, 74611)]}