How to handle missing on dictionary

#python #datastructure #datamodel #programming #language

__missing__ deal with keys when its nos presented on the dict
Try to use Inheritance From Collections.UserDict instead of dict because
- It has already some methods implemented, __get__ and __update__
- it uses a self.data variable, which is a dict, to store values and key, avoiding recursion on __setitem__ method and simplify __contains__.
Key must be hashable: Hashable

class StrKeyDict0(dict): # Using dict as superclass

    def __missing__(self, key):
        if isinstance(key, str):
            raise KeyError(key)
        return self[str(key)] # Transforming into string to avoid recursion

	def get(self, key, default=None):
        try:
            return self[key]
        except KeyError:
            return default

    def __contains__(self, key):
        return key in self.keys() or str(key) in self.keys()

Now using UserDict for the difference:

class StrKeyDict(collections.UserDict):

    def __missing__(self, key):
        if isinstance(key, str):
            raise KeyError(key)
        return self[str(key)]

    def __contains__(self, key):
        return str(key) in self.data # self.data object storing key and values

    def __setitem__(self, key, item):
        self.data[str(key)] = item

References

Ramalho, 2022, p83-96