Converting a list to a set changes element order

Question

Recently I noticed that when I am converting a list to set the order of elements is changed and is sorted by character.

Consider this examp

Answer 1

In case you have a small number of elements in your two initial lists on which you want to do set difference operation, instead of using collections.OrderedDict which complicates the implementation and makes it less readable, you can use:

# initial lists on which you want to do set difference
>>> nums = [1,2,2,3,3,4,4,5]
>>> evens = [2,4,4,6]
>>> evens_set = set(evens)
>>> result = []
>>> for n in nums:
...   if not n in evens_set and not n in result:
...     result.append(n)
... 
>>> result
[1, 3, 5]

Its time complexity is not that good but it is neat and easy to read.