Nameerror: name 'h' is not defined

So I am trying to write a small script in python that will differentiate inputs, and when the appropriate input is given, an int, it will give the correlating answer. I know there are a number of posts on this topic that are similar but I was having trouble finding my answer. Here is what I have.

oktas = input("Oktas: ")

def sky_condition(oktas):
   if isinstance(oktas, int) == True:
      if oktas == 0:
         print ("CLR")
      elif oktas == 1 or oktas == 2:
         print ("FEW")
      elif oktas == 3 or oktas == 4:
         print ("SCT")
      elif oktas >= 5 and oktas <= 7:
         print ("BKN")
      elif oktas == 8:
         print ("OVC")
      elif oktas < 0 or oktas > 8:
         raise ValueError("Oktas provided are above or below the allowed limits.")
   elif isinstance(oktas, int) == False:
      raise NameError("You suck at following instructions.")

skycondition(oktas)

When you put in an int or a str(as in something in "quotation marks") then it processes everything as it should. However if I just put a letter or word without quotation marks, for example h, it raises the error

NameError: name 'h' is not defined 

It produces the error I want but not how I wanted it. How can I code it so it will raise the error how I want it?