Change the name of a key in dictionary

Easily done in 2 steps:

dictionary[new_key] = dictionary[old_key]
del dictionary[old_key]

Or in 1 step:

dictionary[new_key] = dictionary.pop(old_key)

which will raise KeyError if dictionary[old_key] is undefined. Note that this will delete dictionary[old_key].

>>> dictionary = { 1: 'one', 2:'two', 3:'three' }
>>> dictionary['ONE'] = dictionary.pop(1)
>>> dictionary
{2: 'two', 3: 'three', 'ONE': 'one'}
>>> dictionary['ONE'] = dictionary.pop(1)
Traceback (most recent call last):
  File "<input>", line 1, in <module>
KeyError: 1

if you want to change all the keys:

d = {'x':1, 'y':2, 'z':3}
d1 = {'x':'a', 'y':'b', 'z':'c'}

In [10]: dict((d1[key], value) for (key, value) in d.items())
Out[10]: {'a': 1, 'b': 2, 'c': 3}

if you want to change single key: You can go with any of the above suggestion.

pop'n'fresh

>>>a = {1:2, 3:4}
>>>a[5] = a.pop(1)
>>>a
{3: 4, 5: 2}
>>> 

In python 2.7 and higher, you can use dictionary comprehension: This is an example I encountered while reading a CSV using a DictReader. The user had suffixed all the column names with ':'

ori_dict = {'key1:' : 1, 'key2:' : 2, 'key3:' : 3}

to get rid of the trailing ':' in the keys:

corrected_dict = { k.replace(':', ''): v for k, v in ori_dict.items() }