Mentat

The only reference I have found is here - https://github.com/pallets-eco/blinker/issues/52.

Here is the code where the error occurs:

def remove(weak, self=self):
    """Set self.isDead to True when method or instance is destroyed.""" 
    methods = self.deletion_methods[:]
    del self.deletion_methods[:]
    try:
        del self.__class__._all_instances[self.key]
        except KeyError:
            pass
        for function in methods:
            try:
                if callable(function):
                    function(self)
            except Exception:
                try:
                    traceback.print_exc()
                except AttributeError:
                ...

I removed the try/catch block and I found out that a similar error occurs: NameError: name 'callable' is not defined.

Then, I put dir(__builtins__) in the code, which showed this:

['__class__', '__contains__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'clear', 'copy', 'fromkeys', 'get', 'items', 'keys', 'pop', 'popitem', 'setdefault', 'update', 'values']

For some reason, type(__builtins__) is <class 'dict'> and not <class 'module'> as I was expecting.

As it is written in [1]

As an implementation detail, most modules have the name builtins made available as part of their globals. The value of builtins is normally either this module or the value of this module’s dict attribute. Since this is an implementation detail, it may not be used by alternate implementations of Python.

__builtins__ can actually be dictionary.

[1] https://docs.python.org/3/library/builtins.html