[Tutor] Sets question

[Peter Otten]

Phil wrote:

> Another question I'm afraid.
> 
> If I want to remove 1 from a set then this is the answer:
> 
> set([1,2,3]) - set([1])
> 
> I had this method working perfectly until I made a change to cure another
> bug.
> 
> So, I have a set represented in the debugger as {1,2,3} and again I want
> to remove the one. Only this time the one set is represented as {'1'} and,
> of course {'1'} is not in the set {1,2,3}.
> 
> Ideally, I would like {'1'} to become {1}. Try as I may, I have not
> discovered how to remove the '' marks. How do I achieve that?
 
If your code now looks like this

>>> s = {1, 2, 3}
>>> v = "1"
>>> s = s - set([int(v)])
>>> s
{2, 3}

or this

>>> s = {1, 2, 3}
>>> s = s - {int(v)}
>>> s
{2, 3}

I'd like to bring to your attention the discard() method

>>> s = {1, 2, 3}
>>> s.discard(int(v))
>>> s
{2, 3}

which allows you to avoid building the throwaway single-entry set.