蟒蛇。 将新数字覆盖到矩阵的列中

Question

I have data set which has 44000 rows and 5 columns. What I want to do is to erase all the numbers in the second column and to put new numbers there in an incremental order but every other column remains the same as before. For example, first row for that column is 0.001, second row 0.003 and the third row is 0.005 and so on.

How can I implement in Python code? I am still not quite skillful in Python.

I appreciate your helps in advance.

Answer 1

I will explain with an example, for now let me take this list. Your matrix can be thought of as a 2-d list.

let my list be L= [[0,0,0],[0,0,0],[0,0,0]]. This is 3x3 matrix. Assuming that The second column of every row needs to be uniformly incremented by 2, you can try this.

l = [[0,0,0],[0,0,0],[0,0,0]]
inc=0

for i in l:
    i[1]=inc+2
    init=i[1]

print(l)

For every row in the matrix, modify the second column. Use a variable (incr) to track the increments. At the first iteration, the second column of row 1 will be '2'. Once the value is modified, then update the increment variable to the new value, so that it will add your incremental value to this new value in the next iteration. This is what happens.

Iteration 1:
row1 before modifying is [0,0,0]. Then replace the second column with incr+2 (incr is 0 at first, so i[1] becomes 2). Then incr = i[1] will make incr = 2. So now row1 after modifying is [0,2,0].

Iteration 2: row2 before modifying is [0,0,0] . Then replace the second column with incr+2 (incr value changed to 2 in the previous iteration. So now i[1] is incr+2 which is 2+2=4). Then incr = i[1] will make incr=4. So now, row2 after modifying is [0,4,0].

This keeps repeating.