Filling a 2D matrix in numpy using a for loop
First you have to install numpy using
$ pip install numpy
Then the following should work
import numpy as np
n = 100
matrix = np.zeros((n,2)) # Pre-allocate matrix
for i in range(1,n):
matrix[i,:] = [3*i, i**2]
A faster alternative:
col1 = np.arange(3,3*n,3)
col2 = np.arange(1,n)
matrix = np.hstack((col1.reshape(n-1,1), col2.reshape(n-1,1)))
Even faster, as Divakar suggested
I = np.arange(n)
matrix = np.column_stack((3*I, I**2))
This is very pythonic form to produce a list, which you can easily swap e.g. for np.array, set, generator etc.
n = 10
[[i*3, i**2] for i, i in zip(range(0,n), range(0,n))]
If you want to add another column it's no problem. Simply
[[i*3, i**2, i**(0.5)] for i, i in zip(range(0,n), range(0,n))]