Sympy：无法确定关系的真值

Question

from sympy import *

class Example:
    def __init__(self):
        self.data = {
            'sensor1': 0,
            'sensor2': 0,
            'sensor3': 0
        }
        self.registry = {
            '678985': {"data": [{"MID": "sensor1", "D": 50}]},
            '123454': {"data": [{"MID": "sensor2", "D": 5}]},
            '345609': {"data": [{"MID": "sensor3", "D": 500}]}
        }
        self.symbols = {sensor_id: symbols(sensor_id) for sensor_id in self.data.keys()}

    def evaluate_expression(self, expression):
        try:
            for sensor_id, sensor_info in self.registry.items():
                for modality in sensor_info["data"]:
                    m_id = modality["MID"]
                    data = modality["D"]
                    if m_id in self.data:
                        self.data[m_id] = data
    
            expression = expression.replace('&&', 'and').replace('||', 'or').replace('!', 'not')
            sympy_expr = sympify(expression, locals=self.symbols) #parsing
            substitutions = {self.symbols[key]: value for key, value in self.data.items()}
            substituted_expr = sympy_expr.subs(substitutions) #substituting the value from the registry
            result = substituted_expr.simplify()
            # result = bool(substituted_expr)
            return result
        except Exception as e:
            raise ValueError(f"Failed to evaluate expression:{expression} as: {e}")

a = Example()
e = "sensor1 > 10 && sensor1 <= 100 && sensor2 == 2 || sensor3 < 1000 && sensor3 > 400"
a.evaluate_expression(e)

我发送了要通过此检查的表达式

sensor1> 10 && sensor1 <=100 && sensoe2 ==2 || sensor3 < 1000 && sensor3 > 400

我更改了符号并将其与

and, not, or

相关联，但它说无法确定关系的真值

Answer 1

您正在尝试解析此字符串：

s = 'sensor1 > 10 and sensor1 <= 100 and sensor2 == 2 or sensor3 < 1000 and sensor3 > 400'

使用

and

和

or

会强制进行布尔计算，这对于符号表达式来说会失败。使用

&

和

|

代替，也使用

Eq

而不是

==

:

In [30]: s = '(sensor1 > 10) & (sensor1 <= 100) & Eq(sensor2, 2) | (sensor3 < 1000) & (sensor3 > 400)'

In [31]: parse_expr(s)
Out[31]: (sensor₃ > 400 ∧ sensor₃ < 1000) ∨ (sensor₂ = 2 ∧ sensor₁ ≤ 100 ∧ sensor₁ > 10)