如何检查变量的值是否已更改 [英] How to check if a variable's value has changed

问题描述

如果我有一个变量:

var = 5

我想在变量值变化时检测并跳转到一个函数，所以如果var不等于之前的值，我想跳转到一个函数.>

最简单的方法是什么?

另一个例子:

from datetime import datetime导入时间定义解除引用():currentMinute = datetime.now().minute检查分钟(当前分钟)def checkMinute(currentMinute):#如果 currentMinute 已更改，请执行以下操作:打印一些东西()def printSomething():打印分钟已更新"定义主():而(1):解除引用()如果 __name__ == '__main__':主要的()

解决方案

以@HelloWorld 的回答和@drIed 的评论为基础:一个不错的方法是将其包装到一个类中.

例如:

类观察者:"一个简单的类，设置为监视其变量."def __init__(self, value):self.variable = 值def set_value(self, new_value):如果 self.variable != new_value:self.pre_change()self.variable = new_valueself.post_change()def pre_change(self):pass # 在变量即将改变之前做一些事情def post_change(self):pass # 在变量改变后立即执行

If I have a variable:

var = 5

I want to detect and jump to a function when the value of the variable changes, so if var is not equal to the value it was before, I want to jump to a function.

What is the easiest way to do this?

Another example:

from datetime import datetime
import time


def dereferentie():
    currentMinute = datetime.now().minute
    checkMinute(currentMinute)

def checkMinute(currentMinute):

    #if currentMinute has changed do:
        printSomething()

def printSomething():
    print "Minute is updated"


def main():
    while (1):
        dereferentie()


if __name__ == '__main__':
    main()

解决方案

Building on @HelloWorld's answer and @drIed's comment: A nice way would be, to wrap this into a class.

For example:

class Watcher:
    """ A simple class, set to watch its variable. """
    def __init__(self, value):
        self.variable = value
    
    def set_value(self, new_value):
        if self.variable != new_value:
            self.pre_change()
            self.variable = new_value
            self.post_change()
    
    def pre_change(self):
        pass # do stuff before variable is about to be changed
        
    def post_change(self):
        pass # do stuff right after variable has changed
        

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