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#!/usr/bin/env python
# -*- coding: utf-8 -*-
def evaluate_rpn(expression: str) -> float:
stack = []
for token in expression.split():
if token in "+-*/":
b = stack.pop()
a = stack.pop()
if token == "+":
stack.append(a + b)
elif token == "-":
stack.append(a - b)
elif token == "*":
stack.append(a * b)
else: # token == "/"
stack.append(a / b)
else:
stack.append(float(token))
return stack[0]
if __name__ == "__main__":
rpn_expression = "3 4 + 2 * 1 +"
result = evaluate_rpn(rpn_expression)
print(f"RPN expression: {rpn_expression}")
print(f"Result: {result}")
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