How to get ordered set?

Question

EDIT: Thanks. I assumed sets were ordered since the output is almost in alphabetical order. But yes I want an ordered set.

def create_table(secret):    
    sec = set(secret) 
    alpha = set("abcdefghiklmnopqrstuvwxyz")
    bet = alpha - sec

    newSecret = secret & bet

    print newSecret



 OUTPUT:  set(['A', 'C', 'B', 'E', 'D', 'G', 'F', 'I', 'H', 'K', 'M', 'L', 'O', 'N', 'Q', 'P', 'S', 'R', 'U', 'T', 'W', 'V', 'Y', 'X', 'Z'])

How do I create an ordered set?

Example: If I take the string "mathematics" and the string "abcdefghiklmnopqrstuvwxyz", essentially the new string should be "MATHEICSBDFGKLNOPQRUVWXYZ" (assuming i have the code to uppercase the string). There is no 'J' in this string so it isn't a typo.

I'm trying to take the unique characters from the variable 'secret' and unique characters from the variable 'alpha' and get ordered unique characters from both.

Are you looking for simply unordered, or random selections? – Tom Swifty Oct 21 '13 at 16:40 — Tom Swifty, Oct 21 '13 at 16:40

score 11 · Accepted Answer · answered Oct 21 '13 at 16:42

Python doesn't have an OrderedSet; usually we fake it with an OrderedDict.

For example:

>>> from collections import OrderedDict
>>> s = "mathematics"
>>> alpha = "abcdefghiklmnopqrstuvwxyz"
>>> d = OrderedDict.fromkeys(s+alpha)
>>> d
OrderedDict([('m', None), ('a', None), ('t', None), ('h', None), ('e', None), ('i', None), ('c', None), ('s', None), ('b', None), ('d', None), ('f', None), ('g', None), ('k', None), ('l', None), ('n', None), ('o', None), ('p', None), ('q', None), ('r', None), ('u', None), ('v', None), ('w', None), ('x', None), ('y', None), ('z', None)])
>>> ''.join(d)
'matheicsbdfgklnopqruvwxyz'

This doesn't quite work as well as an OrderedSet would, but is often close enough for government work.

"This doesn't quite work as well as an OrderedSet would, but is often close enough for government work." LOL — sberry, Oct 21 '13 at 16:45

score 0 · Answer 2 · answered Oct 21 '13 at 16:37

It sounds like you want an ordered set, ordered by the first occurrence of the item within the first string, or (for items not present in the first string) the first occurrence of the item within the second string.

Easiest thing to do is to have a set, and an string. Iterate over the first string; for each item, if it's not in the set, add it to the set and append it to the string. Then do the same for the second string.

How to get ordered set?

2 Answers2

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