Python 函数作为参数

Question

我无法将其他函数作为参数传递给另一个函数。

我在单独的文件中有函数 marks_as_done 和 delete_task

tasks.py

def mark_as_done(conn):
    print("marking")
    try:
        id = int(input("Enter id of task: "))
        command = f"UPDATE tasklist SET finish_date='{dt_string}', status='True' WHERE id={id}"
        db_execute(command, conn)
    except ValueError:
        print("Wrong! Enter only number.")

def delete_task(conn):
    print("deleting")
    try:
        id = int(input("Enter id of task: "))
        command = f"DELETE from tasklist WHERE id={id}"
        db_execute(command, conn)
    except ValueError:
        print("Wrong! Enter only number.")

我创建了函数 what_next，其中一些参数是函数。

main.py

def what_next(func1, func2, conn, option1, option2):
    print("Starting what next function")
    try:
        x = int(input(f"\n1 - {option1}\n2 - {option2}\n3 - Back to menu\n4 - Exit from app\nChoose what you want to do: "))
        print(f"First This is x from what next function: {x}")
        match x:
            case 1:
                print(f"This is x from what next function: {x}")
                func1
            case 2:
                print(f"This is x from what next function: {x}")
                func2
            case 3:
                print(f"This is x from what next function: {x}")
                mainFunc()
            case 4:
                print(f"This is x from what next function: {x}")
                conn.close()
                sys.exit()
            case _:
                print("Number out fo range.")
                mainFunc()
    except ValueError:
        print("Wrong! Enter only number.")

我在主函数中调用了这个函数：

main.py

def mainFunc():
    print("\n--------------------------Welcome in ToDoList app!--------------------------")
    while True:
        print("""\nMenu:\n1 - Add task\n2 - Show active tasks\n3 - Show tasks history\n4 - Search taks\n5 - Exit\n""")
        try:
            choose = int(input("Choose what you wany to do: "))
            match choose:
                case 1:
                    while True:
                        add_task(conn)
                        what_next(conn, "Continue", "", None, None)
                case 2:
                    while True:
                        show_active_task(conn)
                        #what_next_temp(conn)
                        what_next(mark_as_done(conn), delete_task(conn), conn, "Mark as done", "Delete task")
                case 3:
                    show_task_history(conn)
                    what_next(conn, "Continue", "", None, None)
                case 4:
                    pass
                case 5:
                    conn.close()
                    sys.exit()
                case _:
                    print("Number out fo range.")
                    mainFunc()
        except ValueError:
            print("Wrong! Enter only number.")

我在这种情况下，当我在主函数中选择“2”并在情况 2 中输入时，show_active_task(conn) 函数被正确调用但之后而不是 what_next、marks_as_done和 delete_task 被执行并且在 what_next

之后

更新

最后，我将 what_next 函数更改为：

def what_next(func1, func2, conn, option1, option2):
    print("Starting what next function") 
    try:
        x = int(input(f"\n1 - {option1}\n2 - {option2}\n3 - Back to menu\n4 - Exit from app\nChoose what you want to do: "))
        print(f"First This is x from what next function: {x}")
        match x:
            case 1:
                print(f"This is x from what next function: {x}")
                func1(conn)
            case 2:
                print(f"This is x from what next function: {x}")
                func2(conn)
            case 3:
                print(f"This is x from what next function: {x}")
                mainFunc()
            case 4:
                print(f"This is x from what next function: {x}")
                conn.close()
                sys.exit()
            case _:
                print("Number out fo range.")
                mainFunc()
    except ValueError:
        print("Wrong! Enter only number.")

我这样称呼它：

what_next(mark_as_done, delete_task, conn, "Mark as done", "Delete task")

Answer 1

what_next(mark_as_done(conn), delete_task(conn), conn, "Mark as done", "Delete task")

这是一个函数调用，你实际上把delete_task(conn)的return值传给了what_next。如果你要传递一个函数本身，只使用它的名字，就像这样：

what_next(mark_as_done, delete_task, conn, "Mark as done", "Delete task")

然后就可以在what_next中调用这些函数了。但是确实可以把conn和函数打包在一起，这叫做“函数闭包”：

what_next(lambda : mark_as_done(conn), lambda : delete_task(conn), conn, "Mark as done", "Delete task")

Python 函数作为参数

Python function as argument

python

arguments

function

parameter-passing

tasks.py

main.py

main.py

更新