Append a list to a list: AttributeError: 'NoneType' object has no attribute 'append'

Question

I want to append a list into another list, but it gives me the error:

AttributeError: 'NoneType' object has no attribute 'append'

Originally I wanted to append the list to an array, but that also didn't work...

Here's my code:

import numpy
board = numpy.array([[0, 0, 0, 0, 0, 0, 0, 0],
                     [0, 0, 0, 0, 0, 0, 0, 0],
                     [0, 0, 0, 0, 0, 0, 0, 0],
                     [0, 0, 0, 1, 2, 0, 0, 0],
                     [0, 0, 0, 2, 1, 0, 0, 0],
                     [0, 0, 0, 0, 0, 0, 0, 0],
                     [0, 0, 0, 0, 0, 0, 0, 0],
                     [0, 0, 0, 0, 0, 0, 0, 0]])

class AI:
    def __init__(self, board):
        self.board = board

    def flank_search(self):
        free = []
        xcoord = 0
        ycoord = 0
        while 0 <= xcoord and xcoord <= 7 and 0 <= ycoord and ycoord <= 7:
            if self.board[xcoord][ycoord] == 0:
                coord1 = [xcoord, ycoord]
                free = free.append([coord1])
                xcoord += 1
                print free
        return free


flank = AI(board)
flank.flank_search()

This is an implementation issue and should be migrated to SO. One of the moderators can do it to prevent duplicate questions. — Adam Zuckerman
– Adam Zuckerman, Commented Apr 7, 2014 at 19:37

Zeroth · Accepted Answer · 2014-04-07 18:56:19Z

2

append doesn't return an object. So you assigned None to the variable free.

answered Apr 7, 2014 at 18:56

Zeroth

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1 Comment

user3508072 Over a year ago

Thank you!! Just realised that myself. Boy do I feel stupid now XD

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