[Python](EN) Remove duplicated elements in list

Post about removing duplicated elements in Python list

Environment and Prerequisite

• Python

Remove Duplicated Elements

• Insert to dictionary as key values and change those to list again.
• By following below methods inserted order in list is preserved.
• Different versions have different methods, so they should be used accordingly. Related things are in Reference.

Python 2.7 or higher

OrderedDict.fromkeys(iterable[, value])

• Returns a dictionary using the given values ​​as key values. If there is a value, the value is set as value for all key values, otherwise it is None.
• OrderedDict: Available starting with Python 2.7
• Inserted elements order in iterable is preserved

Example

ex_list = [3, 4, 5, 6, 10, 1, 4, 5, 7, 8, 1, 5, 9]
from collections import OrderedDict
result = list(OrderedDict.fromkeys(ex_list))
print(result)

[3, 4, 5, 6, 10, 1, 7, 8, 9]

Example

ex_list = ['e', 'e', 'b', 'c', 'a', 'e', 'd', 'd', 'b', 'a']
from collections import OrderedDict
result = list(OrderedDict.fromkeys(ex_list))
print(result)

['e', 'b', 'c', 'a', 'd']

Python 3.7 or higher

dict.fromkeys(iterable[, value])

• Returns a dictionary using the given values ​​as key values. If there is a value, the value is set as value for all key values, otherwise it is None.
• Inserted elements order in iterable is preserved starting with Python 3.7
• Partially supported in 3.6 implementation

Example

ex_list = [3, 4, 5, 6, 10, 1, 4, 5, 7, 8, 1, 5, 9]
result = list(dict.fromkeys(ex_list))
print(result)

[3, 4, 5, 6, 10, 1, 7, 8, 9]

Example

ex_list = ['e', 'e', 'b', 'c', 'a', 'e', 'd', 'd', 'b', 'a']
result = list(dict.fromkeys(ex_list))
print(result)

['e', 'b', 'c', 'a', 'd']

Reference

• https://stackoverflow.com/questions/7961363/removing-duplicates-in-the-lists
• https://docs.python.org/release/2.6/search.html?q=OrderedDict&check_keywords=yes&area=default
• https://docs.python.org/release/2.7/search.html?q=OrderedDict&check_keywords=yes&area=default
• https://www.python.org/dev/peps/pep-0372/
• https://docs.python.org/3/whatsnew/3.6.html#summary-release-highlights
• https://docs.python.org/3/whatsnew/3.7.html#summary-release-highlights