Evaluate Reverse Polish Notation

class Solution:
    def evalRPN(self, tokens: List[str]) -> int:
        tokens.reverse()
        stk = []
        while tokens:
            c = tokens.pop()
            if c in '+-*/':
                if c == '+':
                    c2 = stk.pop()
                    c1 = stk.pop()
                    stk.append(c1 + c2)
                elif c == '-':
                    c2 = stk.pop()
                    c1 = stk.pop()
                    stk.append(c1 - c2)
                elif c == '*':
                    c2 = stk.pop()
                    c1 = stk.pop()
                    stk.append(c1 * c2)
                elif c == '/':
                    c2 = stk.pop()
                    c1 = stk.pop()
                    stk.append(int(c1 / c2))
            else:
                stk.append(int(c))
        return stk.pop()