Combining Tuples into a List

Question

I have a list of tuples:

[(1,2), (5,10), (2,5)]

And I would like to get a list of unique numbers

[1,2,5,10]

May I know how can I achieve that?

Because this is just a simple example I need for the program. — Ashtart, Aug 18 '22 at 15:20
Question: in a comment you said that the order is important, for `[(5,10),(2,5), (1,2)]` should it be `[5, 10, 2, 1]`? — cards, Sep 04 '22 at 00:39

score 1 · Answer 1 · answered Aug 18 '22 at 15:20

1

You can use numpy to do it this way:

import numpy as np

x = [(1,2),(5,10),(2,5)]
result = np.array(x).reshape(-1)

If you want to get unique values, use set() like this:

result = set(np.array(x).reshape(-1))

answered Aug 18 '22 at 15:20

milkwithfish

141
3

Good idea, but the order is important – Ashtart Aug 18 '22 at 15:24
If you mean the order it was in the initial list, instead of `set()` you can do this: `list(dict.fromkeys( ["a", "b", "a", "c", "c"]))` – milkwithfish Aug 18 '22 at 15:35

score 1 · Accepted Answer · answered Aug 20 '22 at 13:01

1

Will this work? I've appended each item to a new list, then use set() to get the unique items

new_lis = []
lis = [(1,2),(5,10),(2,5)]
for x,y in lis:
    new_lis.append(x)
    new_lis.append(y)
    
result = list(set(new_lis))

[1, 2, 10, 5]

answered Aug 20 '22 at 13:01

Adrian Ang

520
5
12

score 1 · Answer 3 · answered Aug 20 '22 at 13:31

1

one-line solution:

tuples_list = [(1,2), (5,10), (2,5)]
res = sorted(list(set(sum(tuples_list, ()))))

answered Aug 20 '22 at 13:31

AmirMohammad Babaei

50
1
7

`sum( , ())` is not designed to chain iterables, see doc – cards Sep 04 '22 at 00:21
...and `sorted` is nonsense: with `[(5,10),(2,5), (1,2)]` you get the same result. The order of insertion should be respected – cards Sep 04 '22 at 00:34

score 1 · Answer 4 · answered Aug 20 '22 at 13:40

1

import itertools

L = [(1,2), (5,10), (2,5)]

flat_no_dupes = set(itertools.chain.from_iterable(L))

Using itertools chain from iterable to flatten the list, and making a set to remove duplicates.

answered Aug 20 '22 at 13:40

TessellatingHeckler

27,511
4
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87

score 0 · Answer 5 · answered Sep 03 '22 at 00:36

0

I strongly suggest you use a set comprehension to achieve this result. The set comprehension iterates over the tuples, then over the values in each tuple. We build a set from these values y.

a = [(1,2), (5,10), (2,5)]
{y for x in a 
   for y in x}
# {1, 2, 10, 5}

answered Sep 03 '22 at 00:36

Chris

26,361
5
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42

Do you know why the order is constant in this case but if I do, for ex `print(set("aBc"))`, then change? – cards Sep 04 '22 at 01:03
In Python, sets do not necessarily preserve order. – Chris Sep 04 '22 at 01:12
ok, but you used a set-comprehension, right? – cards Sep 04 '22 at 01:12
Yes, that is a set comprehension. – Chris Sep 04 '22 at 01:13
So with a comprehension the order is "fixed"? I run it multiple times and did not notice any changes... – cards Sep 04 '22 at 01:15
1

Possibly useful reading: https://stackoverflow.com/questions/9792664/converting-a-list-to-a-set-changes-element-order – Chris Sep 04 '22 at 01:15

score 0 · Answer 6 · answered Sep 04 '22 at 01:11

A version which respects the insertion order:

[(1,2), (5,10),(2,5)] -> [1, 2, 5, 10]

[(5,10), (2,5), (1,2)] -> [5, 10, 2, 1]

l = [(5,10),(2,5), (1,2)]

# flat list
l_flat = [i for pair in l for i in pair]

# dictionary of value-position pairs (1st occurence only)
d = dict.fromkeys(l_flat, None)
for i, v in enumerate(l_flat):
    if d[v] is not None:
        continue
    d[v] = i

# order per position and get values
res = [k for k, _ in sorted(d.items(), key=lambda p: p[1])]

# check result
print(res)

Combining Tuples into a List

6 Answers6