执行八皇后约束代码时无法从csp库导入CSP类的问题

AI 小北

2026-7-20

问题描述

执行以下八皇后问题代码时出现导入错误：

from typing import Dict,List,Optional

from csp import CSP
from constraint import Constraint
from typing import Dict,List,Optional

class QueensConstraint(Constraint[int,int]):
    def __init__(self,columns:List[int])->None:
        super().__init__(columns)
        self.columns: List[int]=columns
            
    def satisfied(self,assignment: Dict[int,int])->bool:
        for q1c,q1r in assignment.items():
            for q2c in range(q1c+1,len(self.columns)+1):
                q2r: int=assignment[q2c]
                if q1r==q2r:
                        return False
                if abs(q1r-q2r)==abs(q1c-q2c):
                        return False
                    
        return True
    
if __name__=="__main__":
    columns: List[int]=[1,2,3,4,5,6,7,8]
    for column in columns:
            rows[column]=CSP(columns,rows)
            csp.add_constraint(QueensConstraint(columns))
            solution: Optional[Dict[int,int]]=csp.backtracking_search()
            if solution is None:
                    print("no solution found.")
            else:
                    print(solution)

错误信息：

ImportError                               Traceback (most recent call last)
Cell In[16], line 3
      1 from typing import Dict,List,Optional
----> 3 from csp import CSP
      4 from constraint import Constraint
      5 from typing import Dict,List,Optional

ImportError: cannot import name 'CSP' from 'csp' (c:\users\xxxxx\appdata\local\programs\python\python38\lib\site-packages\csp\__init__.py)

已安装python-constraint、csp、typing库，但问题仍存在。

解决方法

卸载错误的csp包：你安装的csp第三方库和代码中需要的CSP类不匹配，执行命令卸载：
```
pip uninstall csp
```

确认CSP类的来源：

若你是跟着教程编写代码，这个CSP类通常是教程中自定义的模块，而非第三方库。你需要创建csp.py文件，并实现包含backtracking_search等方法的CSP类，示例实现如下：

from typing import Dict, List, Optional
from constraint import Constraint

class CSP:
    def __init__(self, variables: List[int], domains: Dict[int, List[int]]):
        self.variables = variables
        self.domains = domains
        self.constraints: Dict[int, List[Constraint]] = {}
        for variable in self.variables:
            self.constraints[variable] = []
            if variable not in self.domains:
                raise LookupError("每个变量都必须有对应的定义域")

    def add_constraint(self, constraint: Constraint):
        for variable in constraint.variables:
            if variable not in self.variables:
                raise LookupError("约束中的变量不在CSP变量列表中")
            self.constraints[variable].append(constraint)

    def backtracking_search(self, assignment: Dict[int, int] = None) -> Optional[Dict[int, int]]:
        if assignment is None:
            assignment = {}
        if len(assignment) == len(self.variables):
            return assignment
        unassigned = [v for v in self.variables if v not in assignment]
        first = unassigned[0]
        for value in self.domains[first]:
            local_assignment = assignment.copy()
            local_assignment[first] = value
            if self.is_consistent(local_assignment):
                result = self.backtracking_search(local_assignment)
                if result is not None:
                    return result
        return None

    def is_consistent(self, assignment: Dict[int, int]) -> bool:
        for constraint_list in self.constraints.values():
            for constraint in constraint_list:
                if not constraint.satisfied(assignment):
                    return False
        return True

若想直接使用python-constraint库，需调整代码适配其API，该库的约束定义和搜索方法与你当前代码结构不同。

修正主函数逻辑错误：原代码中rows未定义，且循环创建CSP对象的逻辑错误，修正后的主函数如下：

if __name__=="__main__":
    columns: List[int] = [1,2,3,4,5,6,7,8]
    # 为每个列定义可行的行范围
    rows: Dict[int, List[int]] = {col: list(range(1,9)) for col in columns}
    csp = CSP(columns, rows)
    csp.add_constraint(QueensConstraint(columns))
    solution: Optional[Dict[int,int]] = csp.backtracking_search()
    if solution is None:
        print("no solution found.")
    else:
        print(solution)

内容的提问来源于stack exchange，提问作者Hamza Ali