有人可以帮我在python中传递一个函数作为参数吗？

Question

我在 python 中有以下类。我想将函数 get_priority 作为访问对象任务的参数传递。将第二个任务添加到 taskManager 时出现以下错误：

如果 value == array[int(middle)].accessMethod(): AttributeError: Task 实例没有属性“accessMethod”

任务类

class Task:

    def __init__(self,id,name,category="",priority=1):
        self.id = id
        self.name = name
        self.category = category
        self.priority = priority
        self.concluded = False
        self.active_days = 0
        print("Beggining Class")

    def get_name(self):
        return self.name

    def get_category(self):
        return self.category

    def get_priority(self):
        return self.priority

    def set_name(self,name):
        self.name = name

    def set_category(self,category):
        self.category = category

    def set_priority(self,priority):
        self.priority = priority

    def __str__(self):
        return str(self.id) + " | " + self.name + " | " + self.category + " | " + str(self.priority) + " | "

任务管理器类

from task import Task

class TaskManager(object):
    """docstring forTaskManager."""

    def __init__(self):
        print("Initing TaskManager")
        self.taskArray = []

    """Adding task ordered by priority"""
    """Maibe adding a check for autheticity of the object """
    def addTask(self,task):
        if len(self.taskArray) == 0 or self.taskArray[0].get_priority() <= task.get_priority():
            self.taskArray.insert(0,task)
        else:
            index = self.__binarySearchIndex(task.get_priority,self.taskArray,'get_priority')
            self.taskArray.insert(index,task)

    def __binarySearchIndex(self,value,array,acessMethod):
        middle = (len(self.taskArray) / 2) if ((len(self.taskArray) % 2) == 0) else (len(self.taskArray) / 2) + 1
        if middle == 1:
            middle = 0
        if value == array[middle].acessMethod():
            return middle
        elif value < array[middle].acessMethod():
            self.__binarySearchIndex(value,array[:middle])
        else:
            self.__binarySearchIndex(value,array[middle:])

    def __str__(self):
        taskString = ""
        for task in self.taskArray:
            taskString = taskString + str(task) + " \n"
        return taskString

Answer 1

使用 getattr 从你传递的字符串中获取函数

method_to_call = getattr(Task, accessMethod)

if value == array[middle].method_to_call():

Answer 2

我实际上采用了另一种方式，而不是通过名称调用方法，我只是创建了一个 lambda 函数来从 Task 对象中提取我想要的任何属性。

class Task:

    def __init__(self,id,name,category="",priority=1):
        self.id = id
        self.name = name
        self.category = category
        self.priority = priority
        self.concluded = False
        self.active_days = 0
        print("Beggining Class")

    def get_name(self):
        return self.name

    def get_category(self):
        return self.category

    def get_priority(self):
        return self.priority

    def set_name(self,name):
        self.name = name

    def set_category(self,category):
        self.category = category

    def set_priority(self,priority):
        self.priority = priority

    def __str__(self):
        return str(self.id) + " | " + self.name + " | " + self.category + " | " + str(self.priority) + " | "

class TaskManager(object):
    """docstring forTaskManager."""

    def __init__(self):
        print("Initing TaskManager")
        self.taskArray = []

    """Adding task ordered by priority"""
    """Maibe adding a check for autheticity of the object """
    def addTask(self,task):
        if len(self.taskArray) == 0 or self.taskArray[0].get_priority() <= task.get_priority():
            self.taskArray.insert(0,task)
        else:
            index = self.__binarySearchIndex(task.get_priority(),self.taskArray, lambda task: task.get_priority())
            self.taskArray.insert(index,task)

    def __binarySearchIndex(self,value,array,accessMethod):
        if len(array) == 0:
            return 0
        middle = (len(self.taskArray) / 2) if ((len(self.taskArray) % 2) == 0) else (len(self.taskArray) // 2) + 1
        if middle == 1:
            middle = 0
        if value == accessMethod(array[middle]):
            return middle
        elif value < accessMethod(array[middle]):
            return middle + self.__binarySearchIndex(value,array[:middle],accessMethod)
        else:
            return middle - self.__binarySearchIndex(value,array[middle:],accessMethod)

    def __str__(self):
        taskString = ""
        for task in self.taskArray:
            taskString = taskString + str(task) + " \n"
        return taskString

if __name__ == "__main__":
    taskA = Task(1, "taskA", priority=2)
    taskB = Task(2, "taskB", priority=1)
    taskC = Task(3, "taskC", priority=1)
    taskD = Task(4, "taskD", priority=3)
    manager = TaskManager()
    manager.addTask(taskA)
    manager.addTask(taskB)
    manager.addTask(taskC)
    manager.addTask(taskD)
    for task in manager.taskArray:
        print(task)

我还帮助调试了您的程序。对于初学者，您对二分搜索的递归调用不会返回值，这是您想要的行为。

Answer 3

根本不传递包含名称的字符串。使用methodcaller 函数。

例如：

from operator import methodcaller


class TaskManager(object):

    def __init__(self):
        self.taskArray = []

    def addTask(self, task):
        if (len(self.taskArray) == 0
            or self.taskArray[0].get_priority() <= task.get_priority():
            self.taskArray.insert(0,task)
        else:
            index = self.__binarySearchIndex(
                task.get_priority(),
                self.taskArray,
                methodcaller('get_priority')
            )
            self.taskArray.insert(index, task)

    def __binarySearchIndex(self, value, array, accessMethod):
        middle = (len(self.taskArray) / 2) if ((len(self.taskArray) % 2) == 0) else (len(self.taskArray) / 2) + 1
        if middle == 1:
            middle = 0
        if value == accessMethod(array[middle]):
            return middle
        elif value < accessMethod(array[middle]):
            self.__binarySearchIndex(value,array[:middle])
        else:
            self.__binarySearchIndex(value,array[middle:])

    ...

如果您简化 Task 类以摆脱不必要的 getter 和 setter：

class Task:

    def __init__(self,id,name,category="",priority=1):
        self.id = id
        self.name = name
        self.category = category
        self.priority = priority
        self.concluded = False
        self.active_days = 0
        print("Beggining Class")

    def __str__(self):
        return str(self.id) + " | " + self.name + " | " + self.category + " | " + str(self.priority) + " | "

那么您可以使用attrgetter 代替methodcaller。

from operator import attrgetter

class TaskManager(object):

    def __init__(self):
        self.taskArray = []

    def addTask(self, task):
        if (len(self.taskArray) == 0
            or self.taskArray[0].get_priority() <= task.get_priority:
            self.taskArray.insert(0,task)
        else:
            index = self.__binarySearchIndex(
                task.get_priority, 
                self.taskArray,
                attrgetter('get_priority')
            )
            self.taskArray.insert(index, task)

    def __binarySearchIndex(self, value, array, accessMethod):
        middle = (len(self.taskArray) / 2) if ((len(self.taskArray) % 2) == 0) else (len(self.taskArray) / 2) + 1
        if middle == 1:
            middle = 0
        if value == accessMethod(array[middle]):
            return middle
        elif value < accessMethod(array[middle]):
            self.__binarySearchIndex(value,array[:middle])
        else:
            self.__binarySearchIndex(value,array[middle:])

    ...