diff --git a/problems/0150.逆波兰表达式求值.md b/problems/0150.逆波兰表达式求值.md
index 2b294337..bcde7d5b 100644
--- a/problems/0150.逆波兰表达式求值.md
+++ b/problems/0150.逆波兰表达式求值.md
@@ -223,17 +223,19 @@ var evalRPN = function(tokens) {
 python3
 
 ```python
-def evalRPN(tokens) -> int:
-    stack = list()
-    for i in range(len(tokens)):
-        if tokens[i] not in ["+", "-", "*", "/"]:
-            stack.append(tokens[i])
-        else:
-            tmp1 = stack.pop()
-            tmp2 = stack.pop()
-            res = eval(tmp2+tokens[i]+tmp1)
-            stack.append(str(int(res)))
-    return stack[-1]
+class Solution:
+    def evalRPN(self, tokens: List[str]) -> int:
+        stack = []
+        for item in tokens:
+            if item not in {"+", "-", "*", "/"}:
+                stack.append(item)
+            else:
+                first_num, second_num = stack.pop(), stack.pop()
+                stack.append(
+                    int(eval(f'{second_num} {item} {first_num}'))   # 第一个出来的在运算符后面
+                )
+        return int(stack.pop()) # 如果一开始只有一个数，那么会是字符串形式的
+
 ```