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

setup2 = dict((k, {'param1': val10, 'param2': val20}.get(k, v))
              for k, v in setup1.iteritems())

This only works if all keys of the update dictionary are already contained in setup1.

If all your keys are strings, you can also do

setup2 = dict(setup1, param1=val10, param2=val20)