thread_inheritence_sol_1.py

"""The challenge here is to make grand children print out the value set by child, without access to modify cannot_modify"""
from threading import Thread, local, current_thread

# solution start
def new_start(self): # need to patch this
    self.parent = current_thread().ident
    old_start(self)
old_start, Thread.start = Thread.start, new_start

class Local(local):
    threads = {}
    def __init__(self):
        parent = getattr(current_thread(), "parent", None)
        self._update_thread_var(self.threads.get(parent, 'default'))

    def _update_thread_var(self, value):
        self._value = value
        self.threads[current_thread().ident] = self._value

    @property
    def value(self):
        return self._value

    @value.setter
    def value(self, value):
        self._update_thread_var(value)

var = Local()
# solution end

def peek(from_name):
    print(f"{from_name}: {var.value}\n", end="")

def master():
    var.value = "master"
    peek("master")
    children = [Thread(target=child, name=name, args=(name,)) for name in ("A", "B")]
    [t.start() for t in children]
    [t.join() for t in children]


def child(name):
    var.value = name
    peek(name)
    cannot_modify(name)

def cannot_modify(name):
    thread = Thread(target=grand_child, name=f"{name}-{0}", args=(f"{name}-{0}",))
    thread.start()
    thread.join()

def grand_child(name):
    peek(name)

master()
"""
master: master
A: A
A-0: A
B: B
B-0: B
"""