Even after reading the examples in the Python documentation I m still don t know method does Can somebody please tell me Here are two instances from the Python documentation

Question

>>> from collections import defaultdict

>>> s = 'mississippi'
>>> d = defaultdict(int)
>>> for k in s:
...     d[k] += 1
...
>>> d.items()
dict_items([('m', 1), ('i', 4), ('s', 4), ('p', 2)])

and

>>> 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])]

The parameters int and list are for what?

Answer 1

Certainly! The defaultdict subclass of the built-in dict class. It overrides one method to set the dictionary's default value if no key is detected. This helps for collections with unknown keys.

The list and int parameters

A factory function creates the default value for a defaultdict. In your examples:

• int: The default factory function returns 0. It's excellent for counting occurrences, like in your first example, where each letter in'mississippi' is a dictionary key and the value is its count.
• list: The default factory function list provides an empty list []. This helps organize objects, like in your second example, where each unique color is a dictionary key and the values are lists of color numbers.

s = 'mississippi'
d = defaultdict(int)  # int returns 0 by default
for k in s:

d[k] += 1  # For each character in s, it adds 1 to its count in the dictionary.
d.items()  

 

Python collections are handled smoothly and efficiently using default dict's int and list as factory methods to build initial values.