How can I use a class instance variable as an argument for a method decorator in Python?

It's not going to work; the decorator is called during class creation time, which is long before an instance is created (if that ever happens). So if your "decorator" needs the instance, you have to do the "decorating" at instantiation time:

def get_decorator(arg1):
    def my_decorator(function):
        print "get_decorator argument: %s" % arg1
        return function
    return my_decorator

class Foo(object):
    def __init__(self, arg1):
        self.var1 = arg1
        self.method1 = get_decorator(self.var1)(self.method1)

    def method1(self):
        print "method1"

foo = Foo("abc")
foo.method1()

Note that I changed the function names according to their meanings; the actual "decorator", i.e. the function that (potentially) modifies the method, is wrapper in your case, not decorator1.

Your “warper” function is actually a decorator, rather than a warper. Your “decorator1” function is a decorator constructor. If you want to have access to self.var1 in runtime you have to make a warper not decorator:

def decorator(function):
  def wrapper(self,*args,**kwargs):
    print "Doing something with self.var1==%s" % self.var1
    return function(self,*args,**kwargs)
  return wrapper

class Foo(object):
  def __init__(self, arg1):
    self.var1 = arg1

  @decorator
  def method1(self):
    print "method1"

foo = Foo("abc")
foo.method1()

If you want to have more generic decorator, it's better idea to declare a callable class:

class decorator:
  def __init__(self,varname):
      self.varname = varname
  def __call__(self,function):
    varname=self.varname
    def wrapper(self,*args,**kwargs):
      print "Doing something with self.%s==%s" % (varname,getattr(self,varname))
      return function(self,*args,**kwargs)
    return wrapper

Using:

  @decorator("var1")