Getting and converting the value of an instance variable

I need to set an instance variable named Qty(which is an integer) by the value of another instance variable named InstanceName(which is a text string).

So I have to convert the text string to a number by using the int() function. What I can't seem to get correct is the syntax for getting InstanceName.

How do I get the text string of the InstanceName variable?

The path would be: Object -> Instance Variable -> Value

int(--what goes here--)

int(self. InstanceName)