Key Rename in Dictionaries

Renaming a dictionary key can be achieved in several ways, depending on the type of dictionary and whether or not you want to maintain the key's position.

Regular Dict

For a regular dictionary, the key can be renamed using the following syntax:

mydict[k_new] = mydict.pop(k_old)

This operation moves the item to the end of the dictionary. If k_new already exists, its value will be overwritten.

OrderedDict (Python 3.7 )

In Python 3.7 , you can maintain the key's position in an OrderedDict by rebuilding the dictionary:

{k_new if k == k_old else k: v for k, v in od.items()}

This can be used to rename a key while preserving the order, such as renaming key 2 to 'two':

>>> d = {0:0, 1:1, 2:2, 3:3}
>>> {"two" if k == 2 else k:v for k,v in d.items()}
{0: 0, 1: 1, 'two': 2, 3: 3}

Immutable Keys

Modifying the key itself, as suggested in the original question, is impractical because keys are usually hashable and therefore immutable. Modifying them would break the dictionary's integrity.