Context
As an exercise, I am creating a Variable class with the intention of representing a logical variable. It is declared as
class Variable(object):
""" Class for emulate logical variables. """
def __init__(self, valor, /, name='std var'):
self.name = name
if isinstance(valor, bool):
self.valor = valor
else:
raise Exception("Class Error: Constructor must receive a bool as first arg. ")
and within this class I override some standar operators and create the essential logical functions; such as and, or, not
def truth(self):
""" Overload de operacion de verdad. """
return self.valor
def __eq__(self, other):
""" Overload del operador =. """
return True if self.valor == other else False
def __not__(self):
""" Overload del operador (not). """
return True if self.valor else False
def __and__(self, other):
""" Overload del operador & (and). """
return True if (self.valor and other) else False
def __or__(self, other):
""" Overload del operador | (or). """
return True if (self.valor or other) else False
def show(self):
return "{} => {}".format(self.name, self.valor)
Problem
Finally I created a test that raises an interesting error that I can't figure it out. This is the test code
def test():
""" Testing proves. """
q = Variable(True, 'q')
p = Variable(False, 'p')
print("\nDadas {} y {} se da que".format(q.show(), p.show()))
# Checking __eq__
assert (q == q) == True
assert (q == p) == False
# Checking __and__
assert (q and q) == True
assert (q and p) == False
assert (p and p) == False
# checking __or__
assert (q or p) == True
assert (q or q) == True
assert (p or p) == False
# checking __not__
assert (not q) == False
assert (not p) == True, f'{p.show()=}'
and it run smoothly until it raises the next error
assert (not p) == True, f'{p.show()=}'
AssertionError: p.show()='p => False'
I know that the error raises cause the sentence (not p) == True is false. The question is, Why?
What I have thought and tried
First I thought that the truth override it wasn't working. So i change al the p entries for p.valor and do
>>> from Module import Variable
>>>
>>> p = Variable(False)
>>> if p.valor:
>>> print("Not works")
>>> else:
>>> print("Or yes")
Or yes
and it works. Then it occurred to me that the problem might be with __not__. So I rewrote it several times without success. So i tried this
>>> p = Variable(True)
>>> # check if its set correctly
>>> print("Y" if p.valor else "N")
Y
>>> # so p.valor its True. Check __not__
>>> not p
False
>>> # here it seems that `__not__` does work, but
>>> p = L.Variable(False)
>>> p.valor
False
>>> print("Y" if p.valor else "N")
N
>>> not p
False
it looks like the function only works when p.valor = True ...
(Edit)
I ... was lost, but not any more.
After DeepSpace's answer, I rewrote the overload functions. So that they were
def __bool__(self):
return self.valor
def __eq__(self, other):
return True if self.valor == other else False
def __not__(self):
return not(self.valor)
def __and__(self, other):
return True if (self and other) else False
def __or__(self, other):
return True if (self or other) else False
And with this, successfully pass all the tests