Remove partially duplicate tuples from list of tuples

Question

I have a list of tuples and need to delete tuples if its 1st item is matching with 1st item of other tuples in the list. 3rd item may or may not be the same, so I cannot use

Answer 1

You should avoid modifying your list in place while iterating over it. Instead, you can use the popular itertools unique_everseen recipe, also available in 3rd party more_itertools. Just use operator.itemgetter in the key argument:

from more_itertools import unique_everseen
from operator import itemgetter

res = list(unique_everseen(L, key=itemgetter(0, 1)))

This solution takes O(n) time, but is generally less efficient than a dictionary-based solution, although it is arguably clearer in its intention.

Answer 2

The usual way is keying a dict off whatever you want to dedupe by, for example:

>>> a = [(0, 13, 'order1'), (14, 27, 'order2'), (14, 27, 'order2.1'), (0, 13, 'order1'), (28, 41, 'order3')] 
>>> print(*{tup[:2]: tup for tup in a}.values()) 
(0, 13, 'order1') (14, 27, 'order2.1') (28, 41, 'order3')

This is O(n) time complexity, superior to O(n log n) groupby based approaches.

Answer 3

You can get the first element of each group in a grouped, sorted list:

from itertools import groupby
from operator import itemgetter

a = [(0, 13, 'order1'), (14, 27, 'order2'), (14, 27, 'order2.1'), (0, 13, 'order1'), (28, 41, 'order3')]

result = [list(g)[0] for k, g in groupby(sorted(a), key=itemgetter(0))]
print(result)