Nagel-Schreckenberg Traffic Simulation Cellular Automata

traffic.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

from itertools import takewhile
from random import random

MAX_VELOCITY = 5
    
def space():
    return " "

def is_space(n):
    return n == space()

def step(source):
    rslt = acceleration(source)
    rslt = slowing_down(rslt)
    rslt = randomize(rslt)
    return move(rslt)

def acceleration(lane):
    return [v + 1 if not is_space(v) and v < MAX_VELOCITY else v
            for v in lane]

def slowing_down(lane):
    rslt = []
    extended_lane = lane + lane
    for i, v in enumerate(lane):
        if is_space(v):
            rslt.append(v)
        else:
            space_ahead = list(takewhile(is_space, extended_lane[i + 1:]))
            new_velocity = min(v, len(space_ahead))
            rslt.append(new_velocity)
    return rslt

def randomize(lane):
    return [v - 1 if not is_space(v) and v >= 1 and random() < 0.1 else v
            for v in lane]
    
def move(lane):
    lane_size = len(lane)
    rslt = [space()] * lane_size
    for i, v in enumerate(lane):
        if is_space(v): continue
        rslt[(i + v) % lane_size] = v
    return rslt
#%%

lane = [space(), space(), 1, space(), 1, 1, space(), space()]
print(lane)
for _ in range(50):
    lane = step(lane)
    print(lane)