Removing duplicate characters from a string

Question

How can I remove duplicate characters from a string using Python? For example, let's say I have a string:

foo = 'mppmt' 

How can I make the string:

foo = 'mpt' 

NOTE: Order is not important

Answer 1

If order does not matter, you can use

"".join(set(foo)) 

set() will create a set of unique letters in the string, and "".join() will join the letters back to a string in arbitrary order.

If order does matter, you can use a dict instead of a set, which since Python 3.7 preserves the insertion order of the keys. (In the CPython implementation, this is already supported in Python 3.6 as an implementation detail.)

foo = "mppmt" result = "".join(dict.fromkeys(foo)) 

resulting in the string "mpt". In earlier versions of Python, you can use collections.OrderedDict, which has been available starting from Python 2.7.

Answer 2

If order does matter, how about:

>>> foo = 'mppmt' >>> ''.join(sorted(set(foo), key=foo.index)) 'mpt'