Update python dictionary (add another value to existing key)

Update python dictionary (add another value to existing key)

Well you can simply use:

d[word] = [1,something]

Or in case the 1 needs to be fetched:

d[word] = [d[word],something]

Finally say you want to update a sequence of keys with new values, like:

to_add = {word: something, word1: something1}

you could use:

for key,val in to_add.items():
    if key in d:
        d[key] = [d[key],val]

You could write a function to do this for you:

>>> d = {word: 1, word1: 2}
>>> def set_key(dictionary, key, value):
...     if key not in dictionary:
...         dictionary[key] = value
...     elif type(dictionary[key]) == list:
...         dictionary[key].append(value)
...     else:
...         dictionary[key] = [dictionary[key], value]
... 
>>> set_key(d, word, 2)
>>> set_key(d, word, 3)
>>> d
{word1: 2, word: [1, 2, 3]}

Alternatively, as @Dan pointed out, you can use a list to save the data initially. A Pythonic way if doing this is you can define a custom defaultdict which would add the data to a list directly:

>>> from collections import defaultdict
>>> d = defaultdict(list)
>>> d[1].append(2)
>>> d[2].append(2)
>>> d[2].append(3)
>>> d
defaultdict(<type list>, {1: [2], 2: [2, 3]})

Update python dictionary (add another value to existing key)

It will be easiest if you always use lists, even when you just have a single value. It will just be a list of length 1.

>>> d = {a: [1], b: [2]}
>>> d
{a: [1], b: [2]}
>>>
>>> d[a].append(5)
>>> d
{a: [1, 5], b: [2]}