Question

I’m looking for a Python function similar to nubBy in Haskell, which removes duplicate but with a different equality test.

The function would take the equality test and the list as parameters, and would return the list of elements with no duplicates.

Example:

In [1]: remove(lambda x, y: x+y == 12, [2, 3, 6, 9, 10])
Out[1]: [2,3,6]

For example, here (2 and 10) and (9 and 3) are duplicates. I don’t care if the output is [10, 9, 6] or [2, 3, 6].

Is there an equivalent built-in function in Python? If not, what is the best way to efficiently implement it?

Answer 1

There is no built-in method (as the use case is rather esoteric), but you can easily write one:

def removeDups(duptest, iterable):
  res = []
  for e in iterable:
    if not any(duptest(e, r) for r in res):
       res.append(e)
  return res

Now, in the console:

>>> removeDups(lambda x,y: x+y == 10, [2,3,5,7,8])
[2, 3, 5]
>>> removeDups(lambda x,y: x+y == 10, [2,3,6,7,8])
[2, 3, 6]
>>> removeDups(lambda x, y: x+y == 12, [2, 3, 6, 9, 10])
[2, 3, 6]