This solution could be even shorter if python idea of integer division would be the same as for LeetCode.

```
class Solution(object):
def evalRPN(self, tokens):
"""
:type tokens: List[str]
:rtype: int
"""
def sign(a):
return (-1 if a < 0 else 1)
op = {'+':lambda a,b:a+b,'-':lambda a,b:b-a,'*':lambda a,b:a*b,'/':lambda a,b:abs(b)/abs(a)*sign(a)*sign(b)}
st = []
for t in tokens:
if t in op:
st.append(op[t](st.pop(),st.pop()))
else:
st.append(int(t))
return st[0]
```