Output of a random generated list has an extra brackets

Here is my code:

     import random    
     def randnum():
        rando = random.sample(range(1000,9999),1)
        strrando = list(str(rando))
        return strrando

The purpose is being fulfilled, I am generating a list of 4 randomly generated numbers which are turned to type string. The only problem it generates a list that has a set of brackets as strings in the list itself, so it generates 6 strings instead of the 4. I was wondering if anyone could explain to me why this happens?