string object has no attribute 'append' in python

Question

It seems that this code wont run due to an 'str' object has no attribute 'append' error and according to the terminal the problems is due to the following line: new_arr[rows*i + j].append(arr[i][j])

I am trying to convert a matrix to a list.

Any help would be appreciated!

def two_d_translate(arr):

    rows = len(arr)
    cols = len(arr[0])
    total_elements = rows * cols
    new_arr = ['0']*total_elements
    #the number of rows in a mat 
    for i in range(len(arr)):
        for j in range(len(arr[0])):
            new_arr[rows*i + j].append(arr[i][j])
      
    return new_arr

new_arr is a 1-dimensional array of strings, not a 2-dimensional array. — Barmar
– Barmar, Commented Mar 19, 2021 at 19:32
new_arr[rows*i + j] is the string '0'. What are you expecting append() to do? — Barmar
– Barmar, Commented Mar 19, 2021 at 19:33
you're appending onto a string based on the error, so I would assume you're trying to append to a '0' that is in the list. in fact, new_arr is still a 1D array, so when you access it with one subscript, you're accessing a '0' directly instead of, say, a row of '0's. — lionrocker221
– lionrocker221, Commented Mar 19, 2021 at 19:34

Barmar · Accepted Answer · 2021-03-19 19:38:16Z

2

new_arr[rows*i + j] is a string, not a list, you can't append to it.

You don't need to append anything, you just need to replace that element of the list.

new_arr[rows*i + j] = arr[i][j]

But actually there's no need to pre-fill the list and then assign it. You can just append to the list in the loop.

def two_d_translate(arr):
    new_arr = []
    for row in arr:
        for col in row:
            new_arr.append(col)
    return new_arr

answered Mar 19, 2021 at 19:38

Barmar

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Comments

omuthu · Accepted Answer · 2021-03-19 19:40:05Z

0

new_arr is allocated with string values instead of 2d array

new_arr = [[] for i in range(total_elements)]

edited Mar 19, 2021 at 19:40

answered Mar 19, 2021 at 19:35

omuthu

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