COLLECTIONS.DEFAULTDICT(set)

From collections import defaultdict

>>> s = [('yellow', 1), ('blue', 2), ('yellow', 3), ('blue', 4), ('red', 1)]
>>> d = defaultdict(list)
>>> for k, v in s:
...     d[k].append(v)
...
>>> d.items()
[('blue', [2, 4]), ('red', [1]), ('yellow', [1, 3])]

Source: docs.python.org

COLLECTIONS.DEFAULTDICT(set)

defaultdict means that if a key is not found in the dictionary,
then instead of a KeyError being thrown, a new entry is created. 
The type of this new entry is given by the argument of defaultdict.

For example:

somedict = {}
print(somedict[3]) # KeyError

someddict = defaultdict(int)
print(someddict[3]) # print int(), thus 0

>>> from collections import defaultdict

Similar codes

8 votes108 views3 answers
How to install whl file in python
Python
1 vote67 views1 answer
In array number of dictionaries python
Python
2 votes110 views4 answers
Python hash
Python
0 vote106 views1 answer
No module named 'ann_visualizer'
Python
0 vote125 views1 answer
Return tuples form functions in Python
Python
7 votes117 views4 answers
Numpy normalize
Python
-1 vote110 views2 answers
Do not show figure matplotlib
Python
15 votes124 views1 answer
Importing file from another folder python
Python
3 votes114 views1 answer
Python how to find the highest number in a dictionary
Python
5 votes109 views1 answer
Check is lowercase
Python