compacting a mutable sequence

[Larz60+]

there's zlib:

import zlib


class TryZlibBz2:
    def __init__(self):
        your_text = str.encode('i am looking for some already existing implementation of this logic i am ready to implement for myself, if necessary. i want to "compact" a mutable sequence by removing duplicates, keeping the order of both the unique items and each first item of duplicates. converting to a set loses the original order, so it is not an option to convert to a set and convert back, but maybe a set can be used to help detect duplicates in an implementation. anyone know of an existing implementation?')
        compressed = self.zlib_encode(your_text)
        print(f'orig len: {len(your_text)}, len compressed: {len(compressed)}')
        print(f'\n{self.zlib_decode(compressed).decode()}')

    def zlib_encode(self, text):
        return zlib.compress(text)

    def zlib_decode(self, enctext):
        return zlib.decompress(enctext)

if __name__ == '__main__':
    TryZlibBz2()

results:

Output:
orig len: 484, len compressed: 263

i am looking for some already existing implementation of this logic i am ready to implement for myself, if necessary. i want to "compact" a mutable sequence by removing duplicates, keeping the order of both the unique items and each first item of duplicates. converting to a set loses the original order, so it is not an option to convert to a set and convert back, but maybe a set can be used to help detect duplicates in an implementation. anyone know of an existing implementation?