"""Companion code to https://realpython.com/simulation-with-simpy/

'Simulating Real-World Processes With SimPy'

Python version: 3.7.3

SimPy version: 3.0.11

"""

import simpy

import random

import statistics

wait_times = []

class Theater(object):

def __init__(self, env, num_cashiers, num_servers, num_ushers):

self.env = env

self.cashier = simpy.Resource(env, num_cashiers)

self.server = simpy.Resource(env, num_servers)

self.usher = simpy.Resource(env, num_ushers)

def purchase_ticket(self, moviegoer):

yield self.env.timeout(random.randint(1, 3))

def check_ticket(self, moviegoer):

yield self.env.timeout(3 / 60)

def sell_food(self, moviegoer):

yield self.env.timeout(random.randint(1, 5))

def go_to_movies(env, moviegoer, theater):

# Moviegoer arrives at the theater

arrival_time = env.now

with theater.cashier.request() as request:

yield request

yield env.process(theater.purchase_ticket(moviegoer))

with theater.usher.request() as request:

yield request

yield env.process(theater.check_ticket(moviegoer))

if random.choice([True, False]):

with theater.server.request() as request:

yield request

yield env.process(theater.sell_food(moviegoer))

# Moviegoer heads into the theater

wait_times.append(env.now - arrival_time)

def run_theater(env, num_cashiers, num_servers, num_ushers):

theater = Theater(env, num_cashiers, num_servers, num_ushers)

for moviegoer in range(3):

env.process(go_to_movies(env, moviegoer, theater))

while True:

yield env.timeout(0.20) # Wait a bit before generating a new person

moviegoer += 1

env.process(go_to_movies(env, moviegoer, theater))

def get_average_wait_time(wait_times):

average_wait = statistics.mean(wait_times)

# Pretty print the results

minutes, frac_minutes = divmod(average_wait, 1)

seconds = frac_minutes * 60

return round(minutes), round(seconds)

def get_user_input():

num_cashiers = input("Input # of cashiers working: ")

num_servers = input("Input # of servers working: ")

num_ushers = input("Input # of ushers working: ")

params = [num_cashiers, num_servers, num_ushers]

if all(str(i).isdigit() for i in params): # Check input is valid

params = [int(x) for x in params]

else:

print(

"Could not parse input. Simulation will use default values:",

"\n1 cashier, 1 server, 1 usher.",

)

params = [1, 1, 1]

return params

def main():

# Setup

random.seed(42)

num_cashiers, num_servers, num_ushers = get_user_input()

# Run the simulation

env = simpy.Environment()

env.process(run_theater(env, num_cashiers, num_servers, num_ushers))

env.run(until=90)

# View the results

mins, secs = get_average_wait_time(wait_times)

print(

"Running simulation...",

f"\nThe average wait time is {mins} minutes and {secs} seconds.",

)

if __name__ == "__main__":

main()