Building unique comma-delimited list?

[Duncan Booth]

Roy Smith wrote:

> The best I've come up with is the following.  Can anybody think of a
> simplier way?
> 
> --------------------
> words = ["foo", "bar", "baz", "foo", "bar", "foo", "baz"]
> 
> # Eliminate the duplicates; probably use set() in Python 2.4
> d = dict()
> for w in words:
>         d[w] = w
> 
> if d.has_key ("foo"):
>         newWords = ["foo"]
>         del (d["foo"])
> else:
>         newWords = []
> 
> for w in d.keys():
>         newWords.append (w)
> 
> s = ', '.join (newWords)
> print s
> --------------------
> 

You need to make the dictionary and list types work harder for you. They 
have a variety of methods you might find useful.

>>> words = ["foo", "bar", "baz", "foo", "bar", "foo", "baz"]
>>> distinguished = ["foo"]
>>> d = dict.fromkeys(words, True)
>>> newwords = [ w for w in distinguished if d.pop(w, False) ]
>>> newwords.extend(d.keys())
>>> newwords
['foo', 'baz', 'bar']
>>>