Array of Chars to String

[Michael Spencer]

James Stroud wrote:
> Hello,
> 
> I am looking for a nice way to take only those charachters from a string that 
> are in another string and make a new string:
> 
> 
>>>>astr = "Bob Carol Ted Alice"
>>>>letters = "adB"
>>>>some_func(astr,letters)
> 
> "Bad"
> 
> I can write this like this:
> 
> astr = "Bob Carol Ted Alice"
> letters = "adB"
> 
> import sets
> alist = [lttr for lttr in astr if lttr in Set(letters)]
> newstr = ""
> for lttr in alist:
>   newstr += lttr
> 
> But this seems ugly. I especially don't like "newstr += lttr" because it makes 
> a new string every time. I am thinking that something like this has to be a 
> function somewhere already or that I can make it more efficient using a 
> built-in tool.
> 
> Any ideas?
> 
> James
> 
How about:
  >>> astr = "Bob Carol Ted Alice"
  >>> letters = "adB"
  >>> "".join(letter for letter in astr if letter in set(letters))
  'Bad'
  >>>
Michael