Python boolean list with fixed-ordered elements

Question

I am trying to make some binary singal system by boolean variables I named with LIGHTx.

LIGHT1 = True
LIGHT2 = True
LIGHT3 = False
LIGHT4 = False

Next, I nest these variables into a list for future calculation,

signal = [LIGHT1, LIGHT2, LIGHT3, LIGHT4]

Currently I am using the idea from Python: Boolean List to Binary String and Convert base-2 binary number string to int to convert the list to int number which is my signal. Here, [1,1,0,0] means 12.

In [97]: boolList2BinString(signal)
Out[97]: 12

My questions are:

1. How can I automatically updating the elements of "signal" by updating the value of the LIGHTs, rather than running signal = [LIGHT1, LIGHT2, LIGHT3, LIGHT4] again and again? Whitch means, in the rest of my codes, I only need to run LIGHTx = xxxx and boolList2BinString(signal). (Maybe some way like pointer of C++ ?)
2. If it is impossible with question 1, is there any way that I can fix the order of the LIGHTs in the list?

[Update]

Please exclude the way that building the 'signal' list inside the 'boolList2BinString' function.

Original:

def boolList2BinString(lst):
    return int('0b' + ''.join(['1' if x else '0' for x in lst]), 2)

Building inside:

def boolList2BinString():
    osignal = [LIGHT1 , LIGHT2 , LIGHT3 , LIGHT4 ]
    return int('0b' + ''.join(['1' if x else '0' for x in signal ]), 2)

Thanks in advance!

Answer 1

Perhaps you just need some sort of wrapper.

class Light(object):
    def __init__(self, state):
        self.state = state
    def false(self):
        self.state = False
    def true(self):
        self.state = True

LIGHT1 = Light(True)
LIGHT2 = Light(True)
LIGHT3 = Light(False)
LIGHT4 = Light(False)

signal = [LIGHT1, LIGHT2, LIGHT3, LIGHT4]

And then you simply can change states of each lights as LIGHT1.true() or LIGHT1.false() and value in signal list will be changed automatically.

LIGHT1.false()
LIGHT1.state  # False
LIGHT1.true()
LIGHT1.state  # True

The methods naming could be changed, of course.

Answer 2

you can create a class to hold the boolean, then it would act like a pointer

>>> class Light:
...     def __init__(self, value):
...             self.value = value
...     def get(self):
...             return(self.value)
...     def set(self, value):
...             self.value = value

then use light.get() to get the value, or light.set() to set the value

>>> Light1 = light(True)
>>> Light2 = light(False)
>>> lights = [light1, light2]
>>> for l in lights:
...     print(l.get())
... 
True
False

example showing set:

>>> for l in lights:
...     print(l.get())
... 
True
False

>>> light2.set(True)
>>> for l in lights:
...     print(l.get())
... 
True
True
>>> 

Answer 3

You could use a special property class to set bits in an integer.

Here is an example:

class Light(property):
    def __init__(self, rank):
        self.rank= rank
        super(Light, self).__init__(self._get, self._set)
    def _get(self, signal):
        return (signal.value & (1 << self.rank)) != 0
    def _set(self, signal, value):
        if value:
            signal.value |= 1 << self.rank
        else:
            signal.value &= ~(1 << self.rank)

class Signal(object):
    def __init__(self, value=0):
        self.value = value
    l1 = Light(3)
    l2 = Light(2)

You can then use that simply:

>>> s = Signal()
>>> s.value
0
>>> s.l1
False
>>> s.l1 = True
>>> s.l1
True
>>> s.value
8

(Tested on both Python 2.7 and Python 3.5)