Q:

User ranking system

I have written my first code of object oriented Python. Prior to this I have spent a week on learning the concepts and understanding the technique. I would appreciate it somebody reviews this and give suggestion on where I can improve.
I am working through codewars Kata and this code is for the problem.  I am copying the problem here so that some one can see what I have solved.

Write a class called User that is used to calculate the amount that a
  user will progress through a ranking system similar to the one
  Codewars uses.
Business Rules:

A user starts at rank -8 and can progress all the way to 8.
There is no 0 (zero) rank. The next rank after -1 is 1.
Users will complete activities. These activities also have ranks.
Each time the user completes a ranked activity the users rank    progress is  updated based off of the activity's rank
The progress earned from the completed activity is relative to what    the user's  current rank is compared to the rank of the
  activity
A user's rank progress starts off at zero, each time the progress    reaches 100 the user's rank is upgraded to the next level
Any remaining progress earned while in the previous rank will be    applied towards the next rank's progress (we don't throw any progress 
  away). The exception is if there is no other rank left to progress
  towards (Once you reach rank 8 there is no more progression).
A user cannot progress beyond rank 8.
The only acceptable range of rank values is    -8,-7,-6,-5,-4,-3,-2,-1,1,2,3,4,5,6,7,8. Any other value should raise an error.

The progress is scored like so:

Completing an activity that is ranked the same as that of the user's will be worth 3 points
Completing an activity that is ranked one ranking lower than the user's will be worth 1 point
Any activities completed that are ranking 2 levels or more lower than the user's ranking will be ignored
Completing an activity ranked higher than the current user's rank will -accelerate the rank progression. The greater the difference
  between rankings the more the progression will be increased. The
  formula is 10 * d * d where d equals the difference in ranking between
  the activity and the user.

class User():
    rank_vector =[i for i in range(-8,9,1) if ( i!=0)]

    def __init__(self):
        self.rank=-8
        self.progress=0

    def inc_progress(self,kata):
        if kata not in self.rank_vector:
            raise ValueError("Not in the specified Range of features")
        if (self.rank==8):
            progressmeter=0
        elif(self.rank_vector.index(kata) ==self.rank_vector.index(self.rank)):
            progressmeter=self.progress+3
        elif(self.rank_vector.index(kata)==self.rank_vector.index(self.rank)-1):
            progressmeter=self.progress+1
        elif(self.rank_vector.index(kata) <= self.rank_vector.index(self.rank)-2):
            progressmeter=self.progress
        elif(self.rank==-1 and kata==1):
            progressmeter=self.progress+10

        else:
            progressmeter=self.progress+ 10* pow(abs(self.rank_vector.index(kata)-self.rank_vector.index(self.rank)),2)
        progressIndex=list(divmod(progressmeter,100))
        self.progress=progressIndex[1]
        self.rank=self.__updaterank__(progressIndex[0])
        if self.rank==8:
            self.progress=0
        return self.progress

    def __updaterank__(self,level=1):

        if self.rank==8:
            return self.rank
        elif self.rank_vector.index(self.rank)+level > self.rank_vector.index(8):
            self.rank=8
        else:
            self.rank=self.rank_vector[self.rank_vector.index(self.rank)+level]
        return self.rank

A:

On top of what zondo has said you should avoid using parenthesis unnecessarily. There are numerous examples of this:
if (self.rank==8):

can just be:
if self.rank == 8:

also less obvious:
rank_vector =[i for i in range(-8,9,1) if ( i!=0)]

should be:
rank_vector = [i for i in range(-8,9) if i != 0] #Also, no need for the additional "1" parameter.

while we're at it, although you explained it in the description, -8 (nor 8 for what it is worth) isn't the most common of numbers and it seems (without explanation) to be a bit weird.
Maybe somewhere like above rank_vector say:
MIN_RANK = -8
MAX_RANK = 8

And use this when appropriate.

