How to copy a dict and modify it in one line of code

Question

Very often I need to create dicts that differ one from another by an item or two. Here is what I usually do:

setup1 = {\'param1\': val1, 
            \'param         


        

Answer 1

You can write your own class using UserDict wrapper, and simply add dicts like

# setup1 is of Dict type (see below)
setup2 = setup1 + {'param1': val10}

All you have to do is

• Define a new class using UserDict as base class
• Implement __add__ method for it.

---

Something like :

class Dict(dict):
    def __add__(self, _dict):
        if isinstance(_dict, dict):
            tmpdict = Dict(self)
            tmpdict.update(_dict)
            return tmpdict

        else:
            raise TypeError

    def __radd__(self, _dict):
         return Dict.__add__(self, _dict)