### Python 实现搜索条件模块 为了构建一个有效的搜索条件模块，在Python中可以利用面向对象编程(OOP)来设计灵活且可扩展的查询接口。下面展示了一个简单的例子，该示例展示了如何创建一个基础类`SearchCondition`以及几个子类用于表示不同的搜索条件。 #### 定义基本结构 首先定义一个基类 `SearchCondition` 来封装通用属性和方法： ```python class SearchCondition: """Base class for all search conditions.""" def __init__(self, field_name): self.field_name = field_name def to_query(self): raise NotImplementedError("This method should be overridden by subclasses.") ``` 接着为特定类型的搜索条件创建具体的实现，比如等于(`Equal`)、大于(`GreaterThan`)等： ```python from abc import ABCMeta, abstractmethod class Equal(SearchCondition): """Represents an equality condition.""" def __init__(self, field_name, value): super().__init__(field_name) self.value = value def to_query(self): return f"{self.field_name}={self.value}" class GreaterThan(SearchCondition): """Represents a greater than condition.""" def __init__(self, field_name, threshold): super().__init__(field_name) self.threshold = threshold def to_query(self): return f"{self.field_name}>{self.threshold}" ``` 对于更复杂的组合逻辑，则可以通过继承并重写相应的方法来自定义行为。例如，当需要支持AND/OR操作符时，可以这样做： ```python class CompoundCondition(SearchCondition, metaclass=ABCMeta): """Abstract base class for compound (combined) conditions using AND or OR operators.""" operator = None # Must be set in subclass def __init__(self, *conditions): if not isinstance(conditions, tuple) and any(not issubclass(type(c), SearchCondition) for c in conditions): raise ValueError('All arguments must inherit from SearchCondition') self.conditions = list(conditions) @abstractmethod def combine_queries(self): pass def add_condition(self, new_cond): if not isinstance(new_cond, SearchCondition): raise TypeError('Can only append instances of SearchCondition.') self.conditions.append(new_cond) class AndCondition(CompoundCondition): """Combines multiple conditions with the logical 'and' operator""" operator = "AND" def combine_queries(self): queries = [c.to_query() for c in self.conditions] joined_conditions = " {} ".format(self.operator).join(queries) return f"({joined_conditions})" class OrCondition(CompoundCondition): """Combines multiple conditions with the logical 'or' operator""" operator = "OR" def combine_queries(self): queries = [c.to_query() for c in self.conditions] joined_conditions = " {} ".format(self.operator).join(queries) return f"({joined_conditions})" ``` 通过这种方式，可以根据实际需求轻松地添加更多种类的过滤器，并且能够方便地管理复杂查询语句之间的关系[^1]。