Add key to dict with setattr() in Python

Question

How can I add a key to an object's dictionary with setattr()? Say I have the fields dictionary defined in my class. From another class I would like to add a key to this dictionary. How do I proceed? setattr(cls, 'fields', 'value') changes the attribute entirely.

Answer 1

You don't, if you need to go down the name lookup route, then you use:

getattr(cls, 'fields')['key'] = 'value'

Answer 2

You should use getattr instead of setattr to do this. Something like.

>>> class TestClass:
        def __init__(self):
            self.testDict = {}


>>> m = TestClass()
>>> m.testDict
{}
>>> getattr(m, "testDict")["key"] = "value"
>>> m.testDict
{'key': 'value'}