Change the name of a key in dictionary

python dictionary sequence
user469652 picture user469652 · Dec 10, 2010 · Viewed 368.2k times · Source

I want to change the key of an entry in a Python dictionary.

Is there a straightforward way to do this?

Answer

moinudin picture moinudin · Dec 10, 2010

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

Related questions

Python not writing full string to file

I am attempting to output an aligned protein sequence to a file, however, the output string is truncated each time I attempt to write the string to file. The string I'm attempting to write is 4603 characters long, and is printed …

Read More
Iterating over dictionaries using 'for' loops

I am a bit puzzled by the following code: d = {'x': 1, 'y': 2, 'z': 3} for key in d: print key, 'corresponds to', d[key] What I don't understand is the key portion. How does Python recognize that it needs only to …

Read More
Check if a given key already exists in a dictionary

I wanted to test if a key exists in a dictionary before updating the value for the key. I wrote the following code: if 'key1' in dict.keys(): print "blah" else: print "boo" I think this is not the …

Read More