I want to create an immutable class like dictionary in python. I have found the following solution on stackoverflow, but this object is value can be updated by using __dict__.update function. Is there way to block this action.

class Immutable(object):
    def __init__(self, **kwargs):
        """Sets all values once given
        whatever is passed in kwargs
        """
        for k, v in kwargs.items():
            object.__setattr__(self, k, v)

    def __setattr__(self, *args):
        """Disables setting attributes via
        item.prop = val or item['prop'] = val
        """
        raise TypeError('Immutable objects cannot have properties set after init')

    def __delattr__(self, *args):
        """Disables deleting properties"""
        raise TypeError('Immutable objects cannot have properties deleted')


x = Immutable(a=5)
print(x.a) # 5 as expected
x.__dict__.update({'a': 7}) # should raise error or update copy of x
print(x.a) # 7, thus object is still mutable

Solution

As DeepSpace has mentioned in the comment to block access to __dict__ by implementing __getattr__.

I have implemented following solution and it worked

class Immutable(object):
    def __init__(self, **kwargs):
        """Sets all values once given
        whatever is passed in kwargs
        """
        for k, v in kwargs.items():
            object.__setattr__(self, k, v)

    def __getattribute__(self, item):
        result = super(Immutable, self).__getattribute__(item)
        if item == '__dict__':
            return dict(**result)
        return result

    def __setattr__(self, *args):
        """Disables setting attributes via
        item.prop = val or item['prop'] = val
        """
        raise TypeError('Immutable objects cannot have properties set after init')

    def __delattr__(self, *args):
        """Disables deleting properties"""
        raise TypeError('Immutable objects cannot have properties deleted')


x = Immutable(a=5)
print(x.a) # 5
x.__dict__.update({'a': 7}) # update value on a copy of dict which has no effect
print(x.a) # 5 this time object value remain same