Check if a given key already exists in a dictionary and increment it

 

Use dict.setdefault():

>>> d = {1: 'one'}
>>> d.setdefault(1, '1')
'one'
>>> d    # d has not changed because the key already existed
{1: 'one'}
>>> d.setdefault(2, 'two')
'two'
>>> d
{1: 'one', 2: 'two'}

from : https://stackoverflow.com/questions/42315072/python-update-a-key-in-dict-if-it-doesnt-exist