Split data in list based on condition

Question

I have following list :

data = ['A1', 'C3', 'B2', 'A2', 'D3', 'C2', 'A3', 'D2', 'C1', 'B1', 'D1', 'B3']

I want to split the list such that

split1 = ['A1', 'C3', 'B2', 'A2', 'C2', 'A3', 'C1', 'B1', 'B3']
split2 = ['D3', 'D2', 'D1']

Constraint is that no item with same prefix(A, B, etc.) can wind up in separate list. The data can be split in any ratio like 50-50, 80-20.

Does this answer your question? [Python: split a list based on a condition?](https://stackoverflow.com/questions/949098/python-split-a-list-based-on-a-condition) — wjandrea, Jul 11 '21 at 19:36
Why does D get split out, but not B and C? What's special about D? — BoarGules, Jul 11 '21 at 20:32
@BoarGules There is nothing special. It's just based on ratio of the split. It can be 50-50 or 80-20. — hackmyacc, Jul 11 '21 at 20:33
Your problem statement said nothing about a ratio. What at happens if the ratio can't be exact? Your example is a 75/25% split. But suppose there was a D4 and no A3. What then? — BoarGules, Jul 11 '21 at 20:37
@BoarGules There will always be equal number of elements (1, 2, 3). — hackmyacc, Jul 11 '21 at 20:39
Maybe you should edit your question to make those additional constraints clear. — BoarGules, Jul 11 '21 at 20:51
I don't get you... would be something like : `split1 = [item for item in data if 'D' in item]` and `split2 = [item for item in data if 'D' not in item]` ? — Carmoreno, Jul 11 '21 at 21:08

sehan2 · Accepted Answer · 2021-07-11T21:20:28.503

1

Here you go:

import numpy as np
data = np.array(['A1', 'C3', 'B2', 'A2', 'D3', 'C2', 'A3', 'D2', 'C1', 'B1', 'D1', 'B3'])

# define some condition
condition = ['B', 'D']
boolean_selection = [np.any([ c in d for c in condition]) for d in data]

split1 = data[boolean_selection]
split2 = data[np.logical_not(boolean_selection)]

edited Jul 11 '21 at 21:20

answered Jul 11 '21 at 20:44

sehan2

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This solution will not work if the list grows or we change the split of the list. It is currently hardcoded to work with 'D' – hackmyacc Jul 11 '21 at 20:58
well then use some variable for 'D' – sehan2 Jul 11 '21 at 21:00
Thanks for the solution but it doesn't work. If I have to take 'C' and 'A' in split2 then this doesn't work. – hackmyacc Jul 11 '21 at 21:17
this way you can use multiple letters as condition – sehan2 Jul 11 '21 at 21:22

Split data in list based on condition

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