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

0 vote186 views1 answer
Python file get text by regular expression
Python
9 votes184 views6 answers
How to declare variables in python
Python
0 vote233 views1 answer
Python warshall algorithm stackoverflow
Python
0 vote203 views1 answer
How to create new header of a dataframe in python
Python
0 vote202 views1 answer
Pandas map using two columns
Python
2 votes195 views2 answers
Speech to text
Python
0 vote189 views1 answer
Remove items from list while iterating python
Python
1 vote175 views3 answers
Check if number is between two numbers python
Python
4 votes184 views2 answers
Pandas to_csv delimiter
Python
0 vote226 views1 answer
Scrape phone numbers from website python
Python