python - When making a set out of sorted list, the output set is not sorted -

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• understanding set() function 5 answers

could please explain me why making set out of sorted list results in set not sorted?

list.sort() should sort list in place, does. set(list) should return unique values of list, does.

but why resulting set not sorted? need make set, turn list2 , sort list2?

(using python 2.7.6)

code:

def longest(s1, s2):     list = []     s = s1 + s2     letter in s:         list.append(letter)     print list     list.sort()     print list     unique = set(list)     print unique     s4 = ""     item in unique:         s4 = s4 + item     print s4     return s4 

console output:

['a', 'r', 'e', 't', 'h', 'e', 'y', 'h', 'e', 'r', 'e', 'y', 'e', 's', 't', 'h', 'e', 'y', 'a', 'r', 'e', 'h', 'e', 'r', 'e'] ['a', 'a', 'e', 'e', 'e', 'e', 'e', 'e', 'e', 'e', 'e', 'h', 'h', 'h', 'h', 'r', 'r', 'r', 'r', 's', 't', 't', 'y', 'y', 'y'] set(['a', 'e', 'h', 's', 'r', 't', 'y']) aehsrty 

a python set nature unordered. may use ordered-set package if order matters.

https://pypi.python.org/pypi/ordered-set

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