Dynamic Array 2D in Python

Question

I want to save some data from Twitter and I would to use a 2-dimensional array in order to save all hashtags in the first row and all external urls in the second one, with dynamic cols.

I've implemented this:

hashtag_extLink = 2 * [[]]

...
...

if field == "hashtag":
    hashtag_extLink[0].append(x)
elif field == "ext_link":
    hashtag_extlink[1].append(y)
else:
    pass

but, when I will print the hashtag_extLink using this statement:

for row in range(len(hashtag_extLink)):
    print("Row %d" % row)
    for col in range(len(hashtag_extLink[row])):
        print(hashtag_extLink[row][col], end='')
    print("")

I get:

Row 0
xy
Row 1
xy

that is the append() function add value to both rows. How can I fix? Have I to use Numpy?

Thank you in advance.

surabhi bhargava · Accepted Answer · 2017-05-30 11:14:40Z

3

Defining a 2D array like this: x = 2 * [[]] puts the same list in both places in the container list as is happening in your case.

Try defining the array like x = [[],[]]

>>> x = [[],[]]
>>> x[0].append(1)
>>> x
[[1], []]

answered May 30, 2017 at 11:14

surabhi bhargava

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1 Comment

Federico Cuozzo Over a year ago

Solved in this way. Thank you very much.

Subhashi · Accepted Answer · 2020-01-21 12:33:38Z

0

If you know the sizes,

ar = []
for i in range(5):
   ar.append([])
   for j in range(2):
       ar[i].append(1)

answered Jan 21, 2020 at 12:33

Subhashi

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Comments

Saurav Bhowmick · Accepted Answer · 2020-12-05 21:02:50Z

0

You can Define Dynamic 2D array and initialized with 0 values

def initialize_array(rows, cols): l1 = [[0 for i in range(cols)] for j in range (rows)] print (l1)

answered Dec 5, 2020 at 21:02

Saurav Bhowmick

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