Remove duplicates and original from list

by

Use a collections.Counter() object, then keep only those values with a count of 1:

from collections import counter

[k for k, v in Counter(lst).items() if v == 1]

This is a O(N) algorithm; you just need to loop through the list of N items once, then a second loop over fewer items (< N) to extract those values that appear just once.

If order is important and you are using Python < 3.6, separate the steps:

counts = Counter(lst)
[k for k in lst if counts[k] == 1]

Demo:

>>> from collections import Counter
>>> lst = ['a', 'b', 'c', 'c', 'c', 'd', 'e', 'e']
>>> [k for k, v in Counter(lst).items() if v == 1]
['a', 'b', 'd']
>>> counts = Counter(lst)
>>> [k for k in lst if counts[k] == 1]
['a', 'b', 'd']

That the order is the same for both approaches is a coincidence; for Python versions before Python 3.6, other inputs may result in a different order.

In Python 3.6 the implementation for dictionaries changed and input order is now retained.

More Related Contents:

  1. How do you remove duplicates from a list whilst preserving order?
  2. Removing duplicates in lists
  3. How do I find the duplicates in a list and create another list with them?
  4. Removing elements that have consecutive duplicates
  5. How do I check if there are duplicates in a flat list?
  6. How do I remove duplicates from a list, while preserving order?
  7. TypeError: unhashable type: ‘list’ when using built-in set function
  8. How can I find same values in a list and group together a new list?
  9. Duplicate each member in a list [duplicate]
  10. Python: Remove Duplicate Items from Nested list
  11. Python: Rename duplicates in list with progressive numbers without sorting list
  12. python remove duplicates from 2 lists
  13. Getting the index of the returned max or min item using max()/min() on a list
  14. Why can tuples contain mutable items?
  15. Find and replace string values in list
  16. How to find most common elements of a list? [duplicate]
  17. How do you pick “x” number of unique numbers from a list in Python?
  18. How to convert list of key-value tuples into dictionary?
  19. Finding index of an item closest to the value in a list that’s not entirely sorted
  20. Python split string into multiple string [duplicate]
  21. How to convert a list to a list of tuples?
  22. How to input matrix (2D list) in Python?
  23. Combining Dictionaries Of Lists In Python
  24. How to get all combination of n binary value? [duplicate]
  25. Convert a columns of string to list in pandas
  26. Indexing a list with an unique index
  27. Why doesn’t assigning to the loop variable modify the original list? How can I assign back to the list in a loop? [duplicate]
  28. Flattening a list recursively [duplicate]
  29. How to sort a 2D list? [closed]
  30. Creating a list in Python with multiple copies of a given object in a single line

Leave a Comment