# Numpy linalg and solving a linear system of equations

We show here how to read a square matrix `A` from a file `A.txt` and a vector `b` from a file `b.txt` and print the solution `x` to the equation `Ax = b`.

 ``` #! /usr/bin/python3 # Define a vector and a matrix and compute the matrix-vector product import numpy as np from numpy import linalg as LA # Read the matrix A = np.loadtxt("A.txt") # Read the rhs vector b = np.loadtxt("b.txt") # Solve the linear system Ax = b x = LA.solve(A,b) # Print the solution print(x) ```

Here are the new features of the code:
 ``` from numpy import linalg as LA ```

The `numpy` package contains a `linalg` subpackage. It is automatically loaded with `numpy`, and it can be accessed with `np.linalg`. But with this command we can access it with `LA` instead and save typing.
 ``` x = LA.solve(A,b) ```

The linear algebra subpackage has functions starting with `np.linalg`. Here we access them with `LA`. The `solve` member of the subpackage that we use here takes a matrix and a vector and solves the linear system.

Try running the code to see the result.