def infix_evaluator(infix_expression: str): token_list = infix_expression.split() print(token_list) pre_dict = {'*': 2, '/': 2, '+': 1, '-': 1} ope_stack = [] num_stack = [] for i in token_list: if i.isdecimal() or '.' in i: num_stack.append(float(i)) elif i in '+-*/': while ope_stack and pre_dict[ope_stack[-1]] >= pre_dict[i]: top = ope_stack.pop() op2 = num_stack.pop() op1 = num_stack.pop() num_stack.append(get_value(top, op1, op2)) ope_stack.append(i) while ope_stack: top = ope_stack.pop() op2 = ope_stack.pop() op1 = ope_stack.pop() ope_stack.append(get_value(top, op1, op2)) return ope_stack[0] def get_value(operator, op1, op2): if operator == '+': return op1 + op2 elif operator == '-': return op1 - op2 elif operator == '*': return op1 * op2 elif operator == '/': return op1 / op2 print(infix_evaluator('2.5 - 3 * 4')),这一段代码那里出现了问题,运行不了
时间: 2024-02-14 19:17:06 浏览: 30
在 `while` 循环中计算表达式的值的时候,有一个地方出现了错误:
```
top = ope_stack.pop()
op2 = ope_stack.pop()
op1 = ope_stack.pop()
```
应该是从 `num_stack` 中取出操作数,而不是从 `ope_stack` 中取出操作符。正确的代码应该是:
```
top = ope_stack.pop()
op2 = num_stack.pop()
op1 = num_stack.pop()
```
修改后的代码如下:
```python
def infix_evaluator(infix_expression: str):
token_list = infix_expression.split()
print(token_list)
pre_dict = {'*': 2, '/': 2, '+': 1, '-': 1}
ope_stack = []
num_stack = []
for i in token_list:
if i.isdecimal() or '.' in i:
num_stack.append(float(i))
elif i in '+-*/':
while ope_stack and pre_dict[ope_stack[-1]] >= pre_dict[i]:
top = ope_stack.pop()
op2 = num_stack.pop()
op1 = num_stack.pop()
num_stack.append(get_value(top, op1, op2))
ope_stack.append(i)
while ope_stack:
top = ope_stack.pop()
op2 = num_stack.pop()
op1 = num_stack.pop()
num_stack.append(get_value(top, op1, op2))
return num_stack[0]
def get_value(operator, op1, op2):
if operator == '+':
return op1 + op2
elif operator == '-':
return op1 - op2
elif operator == '*':
return op1 * op2
elif operator == '/':
return op1 / op2
print(infix_evaluator('2.5 - 3 * 4'))
```
输出结果为 `-9.5`。
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