4.4 Accessing array entries

Array entries are accessed by indexes. In contrast to vector coefficients, two indexes are needed to access matrix coefficients. These are given in one pair of brackets. This distinguishes the array syntax from a list of lists. There, two pairs of brackets are needed to access elements.

M = array([[1., 2.],[3., 4.]])
M[0, 0] # first row, first column: 1.0
M[-1, 0] # last row, first column: 3.0

Let's look now in more detail at the use of double indexes and slices.