Function trigger when a variable change-CodePudding

I'm trying to write a single funcion that turn to true when a variable changes. The script should put the variable in a list and check if it changes. Now, i need to call the function in another loop, so the script have to do one cicle when invoked for i in range(0, 1) Anyway the function doesnt works and the output is always false...any suggestions?
(NOOB)

def change():
    v1 = []
    for i in range(0, 1):
        v1.insert(0, get.value()) #get.value gaves a value when invoked
        if len(v1) > 2:
            if v1[0] != v1[1]:
                v1.clear()
                v1.insert(0, get.value())
                return True
            else:
                return False

CodePudding user response：

You've made this harder than it needs to be. Just store the value you know and wait for it to change.

def change():
    v1 = get.value()
    while get.value() == v1:
        time.sleep(0.5)
    return True

You need the sleep in there, otherwise this will consume 100% of the CPU and your other code won't run. Remember this ONLY works in a thread, which means it's probably not what you really need.

CodePudding user response：

You can use a decorator factory to freeze values:

from functools import partial


def frozen_args(val):
    def my_decorator(wrapped_func):
        return partial(wrapped_func, frozenval=val)
    return my_decorator
    

class Get:
    def __init__(self):
        self.x = 1
    def value(self):
        return self.x

get = Get()

@frozen_args(get.value())
def change(frozenval: int) -> bool:
    return get.value() != frozenval

Testing it:

>>> change()
False
>>> get.x = 3
>>> change()
True

If you ever need to reset the value in testing, remove the decorator from the function definition and use it inline when you need it:

def change(frozenval: int) -> bool:
    return get.value() != frozenval

>>> change_now = frozen_args(get.value())(change)
>>> get.x = 2
>>> change_now()
True
>>> change_now = frozen_args(get.value())(change)
>>> change_now()
False