If I have the following matrix, which the input format is a list of lists:
| B | T | E |
|---|---|---|
| 0 | 1 | 0 |
| 0 | 1 | 1 |
| 0 | 2 | 1 |
| 1 | 2 | 0 |
How can I construct the following python matrix:
0 1
D = [[{1}, {1,2}], 0
[{2}, {}]] 1
Where the elements of D, merge the pairs (B,E) with it’s respective T. Example: (0,1) in the above matrix, have T = 1 and T = 2, so in D matrix it should be a set {1,2}. Since there is no (1,1) pair, it should be a empty set {}.
How could a do that in a “pythonic” way?
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Answer
You can use collections.defaultdict:
from collections import defaultdict
m = [[0, 1, 0], [0, 1, 1], [0, 2, 1], [1, 2, 0]]
d = defaultdict(dict)
for b, t, e in m:
d[b][e] = [t] if e not in d[b] else [*d[b][e], t]
l = {i for b in d.values() for i in b}
result = [[set(k.get(j, [])) for j in l] for k in d.values()]
print(result)
Output:
[[{1}, {1, 2}],
[{2}, set()]]