Modify some elements in 2D python list

Question

My list looks like this:

board = [ [ 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 , 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 , 0 , 0],
      [ 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0] ]

How can I modify some of the elements? E.g.: the first element in each row = 0. I want to replace them with fives. So my list would look like this:

board = [ [ 5 , 0 , 0 , 0 , 0 , 0 , 0 , 0],
      [ 5 , 0 , 0 , 0 , 0 , 0 , 0 , 0],
      [ 5 , 0 , 0 , 0 , 0 , 0 , 0 , 0],
      [ 5 , 0 , 0 , 0 , 0 , 0 , 0 , 0],
      [ 5 , 0 , 0 , 0 , 0 , 0 , 0 , 0],
      [ 5 , 0 , 0 , 0 , 0 , 0 , 0 , 0],
      [ 5 , 0 , 0 , 0 , 0 , 0 , 0 , 0],
      [ 5 , 0 , 0 , 0 , 0 , 0 , 0 , 0] ]

MLavrentyev · Accepted Answer · 2017-04-21 22:38:38Z

1

You can access a specific cell of a 2D array by doing board[r][c], where r is the row and c is the column. For replacing the first column with 5's, you could do:

for row in board:
    row[0] = 5

This iterates over every row in board, and sets the first item in each row to 0.

edited Apr 21, 2017 at 22:38

answered Apr 21, 2017 at 22:27

MLavrentyev

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2 Comments

kaycaborr Over a year ago

And if I get 2 numbers by input and only want to change 1 element? r=int(input("row: ")) c=int(input("column: ")) E.g. r=2 and c=6. So I want board[2][6] to be changed.

MLavrentyev Over a year ago

If you want one specific cell to be changed, you can do board[2][6] = newValue. Replace newValue with the value you want to set there.

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