CODEWITHSUNDEEP
pythonpython-2.7
Liondancer
Liondancer

Reputation: 16469

Nonetype object has no append attribute append list to dict

If i enter in n, a dictionary count_dict of size n+1 will be created with keys 0...n.

I want to parse through a list called binary_list that contains strings of size n that each compose of 0's or 1's. Each parse will count the number of 1's in the string and appendeach string with the number of 1's to the appropriate key

ex:

{0:['000'], 1:['001','010','100'] , 2:['011', '101', '110'] , 3:['111']}

my code to perform this:

count_dict = dict.fromkeys(range(0,n+1))

for element in binary_list:
    count_dict[element.count('1')].append(element)

error"

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "facebook_prob.py", line 23, in sortbit
    count_dict[element.count('1')].append(element)
AttributeError: 'NoneType' object has no attribute 'append'

Upvotes: 2

Views: 5850

Answers (1)

falsetru
falsetru

Reputation: 369064

Without specifying the second argument, values are None by default. (See dict.fromkeys)

>>> n = 3
>>> count_dict = dict.fromkeys(range(0,n+1))
>>> count_dict
{0: None, 1: None, 2: None, 3: None}

In addition to that, values created by dict.fromkeys are shared by all entries.

>>> count_dict = dict.fromkeys(range(0,n+1), [])
>>> count_dict
{0: [], 1: [], 2: [], 3: []}
>>> count_dict[0] is count_dict[1]
True

collections.defaultdict is more appropriate.

>>> from collections import defaultdict
>>> count_dict = defaultdict(list)
>>> count_dict[0].append('000')
>>> count_dict[1].append('001')
>>> count_dict[1].append('010')
>>> count_dict
defaultdict(<type 'list'>, {0: ['000'], 1: ['001', '010']})

Upvotes: 5

Related Questions