List of all unique characters in a string?

Question

I want to append characters to a string, but want to make sure all the letters in the final list are unique.

Example: \"aaabcabccd\" →

Answer 1

The simplest solution is probably:

In [10]: ''.join(set('aaabcabccd'))
Out[10]: 'acbd'

Note that this doesn't guarantee the order in which the letters appear in the output, even though the example might suggest otherwise.

You refer to the output as a "list". If a list is what you really want, replace ''.join with list:

In [1]: list(set('aaabcabccd'))
Out[1]: ['a', 'c', 'b', 'd']

As far as performance goes, worrying about it at this stage sounds like premature optimization.