Cannot rename Python dict key values with pop - Bug?

Question

I cannot rename the Python dict using pop as described below. I've used suggestions from this post. Is this a Python bug? I'm using Python 3.5.2

>>> d = {'a': 'ABC', 'b': 'CDE', 'c': 'KRT'}
>>> for old_key in d.keys():
        d['NEW_KEY_' + old_key] = d.pop(old_key)
>>> d

{'NEW_KEY_NEW_KEY_NEW_KEY_b': 'CDE', 'NEW_KEY_NEW_KEY_a': 'ABC', 'c': 'KRT'}

Answer 1

In Python 3, you have to change for old_key in d.keys() into for old_key in list(d.keys()). That should work because you are iterating over a dynamic entity.