import numpy as np
mat=np.array([[1,2], [3,4]])
# sum columns
np.sum(mat, axis=0)
# sum rows
np.sum(mat, axis=1)
# min of columns
np.min(mat, axis=0)

# delete 1st row
np.delete(mat, 0, axis=0)
# delete 1st column
np.delete(mat, 0, axis=1)