Local variable referencing to the same object of a global variable is changed, but the global is not

Question

I have the following problem: I’m making a Red-Black Tree in Python, and when I delete a root that has only one child, the problem happens, below follows my code

BLACK = 0
RED = 1

class No():

    def __init__(self, valor, pai=None, esquerda=None, direita=None, cor=RED):
        self.valor = valor
        self.esquerda = esquerda
        self.direita = direita
        self.pai = pai
        if pai == None:
            self.cor = BLACK
        else:
            self.cor = cor

    def filho_nao_nulo(self):
        return (self.direita if self.direita != None else self.esquerda)

    def remover(self, valor):
        #global raiz
        no = self
        if no == None:
            return None
        if valor < no.valor:
            no.esquerda.remover(valor)
        elif valor > no.valor:
            no.direita.remover(valor)
        else:
            #o nó encontrado só tem um filho
            if no.direita != None or no.esquerda != None:
                if no.cor == BLACK:
                        #se o nó é a raiz
                        if no.pai == None:
                            if no.esquerda == no.filho_nao_nulo():
                                no = no.esquerda
                                no.cor = BLACK
                            else:
                                no = no.direita
                                no.cor = BLACK                          

raiz = No(12)
raiz.direita = No(14, raiz)
raiz.remover(12)

On reaching the line

no = no.direita

the debug is that way:

When running this line, only the local variable "no" is changed, but the global "root" is not, both of which refer to the same memory address

the node has the memory address of the root right, as it should be done with the root, but the root is not changed.

The strange thing is that this only happens with the root, if the node, for example, was equal to the root.rightita.left, there would be no problem with any operation I wanted to do about that node, it would change both the local variable, and the global one.

I had a similar problem in the AVL tree.

The temporary solution I had was to declare the code

global raiz

at the beginning of the method, and change the root directly. But I read about, and saw that this is not a good practice. Could anyone help me ? Thank you.