在Python中将列添加到2D数组

Question

I'm trying to add an extra column to a 2D array in Python but I'm stuck. I have a 2D array like below:

['000', '101']
['001', '010']
['010', '000']
['011', '100']

Then I swap 2 elements from the 2nd column and have something like this:

['000', '101']
['001', '000']
['010', '010']
['011', '100']

I want to take the last column right now and add it as the 3rd one like this:

['000', '101', '101']
['001', '010', '000']
['010', '000', '010']
['011', '100', '100']

But I only managed to get this:

['000', '101']
['001', '000']
['010', '010']
['011', '100']
101
000
010
100

I'm adding a column like this:

col = column(data,1)
data_res += col

I'm creating an array like this:

with open('data.txt', 'r') as f:
     for line in f:
         line_el = line.split()
         data.append(line_el)

I'm swapping like this:

def swap(matrix, id_l, id_r):
    matrix[id_l][1], matrix[id_r][1] = matrix[id_r][1],matrix[id_l][1]
    return matrix

Any ideas?

Answer 1

Since you are writing your 2D list as a list of lists ( Row Major Order ), adding a column means adding an entry to each row.

It seems you already have some data created like this:

# Create a 2D list
data = [['000', '101'],['001', '010'],['010', '000'],['011', '100']]

So now you could add a new column identical to the last column like this:

# Loop through all the rows
for row in data:
  lastColumn = row[-1]
  # Now add the new column to the current row
  row.append(lastColumn)

Answer 2

A list comprehension can do this quickly. This code doesn't perform the swap, but it looks like you have that working already. :)

data = [['000', '101'],['001', '010'],['010', '000'],['011', '100']]
print [x + [x[1]] for x in data]

# [
#     ['000', '101', '101'],
#     ['001', '010', '010'],
#     ['010', '000', '000'],
#     ['011', '100', '100']
# ]

with open('data.txt', 'r') as f:
    for line in f:
        line_el = line.split()
        data.append([x + [x[1]] for x in line_el])