levywalklike_function

import random
from datetime import datetime
import numpy as np

random.seed(datetime.now())

def direction(probability, last_direction):

    if last_direction == [0, 0]:
        """pick an initial random direction with uniform distribution"""
        direction_xy = polarToCartesian(random.randint(0, 7))
    else:
        last_direction = cartesianToPolar(last_direction)
        low_prob = (1 - probability/100) / 7
        directions_p = [low_prob for p in range(7)]
        directions_p[last_direction] = probability/100
        directions_p /= np.sum(directions_p)
        direction_xy = np.random.choice(range(7), p=directions_p)
        direction_xy = polarToCartesian(direction_xy)

    return(direction_xy)

def polarToCartesian(direction):
    # 0 1 2
    # 7 b 3
    # 6 5 4
    return {
        0: [-1, -1],
        1: [-1,  0],
        2: [-1, +1],
        3: [ 0, +1],
        4: [+1, +1],
        5: [+1,  0],
        6: [+1, -1],
        7: [ 0, -1]
    } [direction]

def cartesianToPolar(direction):
    if direction[0] < 0:
        if direction[1] == -1:
            return 0
        elif direction[1] == 0:
            return 1
        else:
            return 2
    elif direction[0] == 0:
        if direction[1] == -1:
            return 7
        else:
            return 3
    else:
        if direction[1] == -1:
            return 6
        elif direction[1] == 0:
            return 5
        else:
            return 4

### TEST
#for t in range(100):
#    print(direction(50, [1, 0]))