[Tutor] Removing control characters

[Kent Johnson]

On Thu, Feb 19, 2009 at 5:41 PM, Dinesh B Vadhia
<dineshbvadhia at hotmail.com> wrote:
> Okay, here is a combination of Mark's suggestions and yours:

>> # replace unwanted chars in string s with " "
>> t = "".join([(" " if n in c else n) for n in s if n not in c])
>> t
> 'Product ConceptsHard candy with an innovative twist, Internet Archive:
> Wayback Machine. [online] Mar. 25, 2004. Retrieved from the Internet <URL:
> http://www.confectionery-innovations.com>.'
>
> This last bit doesn't work ie. replacing the unwanted chars with " " - eg.
> 'ConceptsHard'.  What's missing?

The "if n not in c" at the end of the list comp rejects the unwanted
characters from the result immediately. What you wrote is the same as
t = "".join([n for n in s if n not in c])

because "n in c" will never be true in the first conditional.

BTW if you care about performance, this is the wrong approach. At
least use a set for c; better would be to use translate().

Kent