Compare several values of pandas dataframe with the same id

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I have an df which has this structure:

         paramter    names   ids
0        0.008        t        1
1        0.349        P1       1
2        0.120        P2       1
3        0.008        t        2
4        0.349        P1       2
5        0.120        P2       2 
6        0.209        t        3
7        0.349        P1       3
8        0.200        P2       3
9        0.209        t        4
10       0.349        P1       4
11       0.200        P2       4
...      ...             ...     ...
3000

I want to extract for each element, with given id, the parameters of P1, P2, t. If all of the parameters of one element are the same as for another element, then I want to add them to the same list. Here 1,2 would be in the same list and 3,4 in another list, because all three values of 1 correspondent to 2 and all three values of 3 correspondent to 4.

I do not know how many different elements I have, so I do not know how may lists I need.

pandas dataframe list python
1 Answers

Use pivot to reshape the dataframe with index as id, columns as names and values as parameter, then use groupby on P1, p2, t and collect ids belonging to same group in list comprehension:

df1 = df.pivot('ids', 'names', 'paramter').reset_index()
ids = [g['ids'].tolist() for _, g in df1.groupby(['P1', 'P2', 't'])]

Details:

print(df1)
names  ids     P1    P2      t
0        1  0.349  0.12  0.008
1        2  0.349  0.12  0.008
2        3  0.349  0.20  0.209
3        4  0.349  0.20  0.209

print(ids)
[[1, 2], [3, 4]]
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