Python script to draw a lorenz attractor with Euler's method.

lorenz_attractor_euler.py

#! /usr/local/bin/python3.6
"""
Lorenz attractor (Euler method)
"""
import sys
import traceback
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D


class LorenzAttractorEuler:
    DT            = 1e-3     # Differential interval
    STEP          = 100000   # Time step count
    X_0, Y_0, Z_0 = 1, 1, 1  # Initial values of x, y, z

    def __init__(self):
        self.res = [[], [], []]

    def exec(self):
        """ Loranz attractor (Euler method) execution """
        try:
            xyz = [self.X_0, self.Y_0, self.Z_0]
            for _ in range(self.STEP):
                l = self.__lorenz(xyz)
                for i in range(3):
                    xyz[i] += self.DT * l[i]
                    self.res[i].append(xyz[i])
            self.__plot()
        except Exception as e:
            raise

    def __lorenz(self, xyz, p=10, r=28, b=8/3.0):
        """ Lorenz equation

        :param  list xyz
        :param  float  p
        :param  float  r
        :param  float  b
        :return list xyz
        """
        try:
            return [
                -p * xyz[0] + p * xyz[1],
                -xyz[0] * xyz[2] + r * xyz[0] - xyz[1],
                xyz[0] * xyz[1] - b * xyz[2]
            ]
        except Exception as e:
            raise

    def __plot(self):
        """ Protting """
        try:
            fig = plt.figure()
            ax = Axes3D(fig)
            ax.set_xlabel("x")
            ax.set_ylabel("y")
            ax.set_zlabel("z")
            ax.set_title("Lorenz attractor (Euler method)")
            ax.plot(self.res[0], self.res[1], self.res[2], lw=1)
            #plt.show()
            plt.savefig("lorenz_attractor_euler.png")
        except Exception as e:
            raise


if __name__ == '__main__':
    try:
        obj = LorenzAttractorEuler()
        obj.exec()
    except Exception as e:
        traceback.print_exc()
        sys.exit(1)