How to set default value to all keys of a dict object in python?

Question

I know you can use setdefault(key, value) to set default value for a given key, but is there a way to set default values of all keys to some value after creating a dict ?

Answer 1

You can use the following class. Just change zero to any default value you like. The solution was tested in Python 2.7.

class cDefaultDict(dict):
    # dictionary that returns zero for missing keys
    # keys with zero values are not stored

    def __missing__(self,key):
        return 0

    def __setitem__(self, key, value):
        if value==0:
            if key in self:  # returns zero anyway, so no need to store it
                del self[key]
        else:
            dict.__setitem__(self, key, value)