a basic implementation of the common "elevator" interview question.

elevators.py

import time

class Elevator:
    def __init__(self):
        self.state = "stand"
        self.doors = "open"
        self.currentFloor = 1
        self.requests = []

    def requestFloor(self, floorNum):
        # only begin moving to floor if currently in 'stand' mode
        if(self.state == "stand"):
            if(floorNum < self.currentFloor):
                self.goDown(floorNum)
            elif(floorNum > self.currentFloor):
                self.goUp(floorNum)
        # if elevator is moving, add to requests to check
        elif(self.state == "up" or self.state == "down"):
            self.requests.append(floorNum)

    def goUp(self, floorNum):
        self.closeDoors()
        self.state = "up"
        # continue going up until floor is reached
        while(self.currentFloor < floorNum):
            self.currentFloor += 1
            # pause for five seconds if a floor we're passing has a request
            if(self.currentFloor in self.requests):
                self.openDoors()
                time.sleep(5)
                self.requests.remove(self.currentFloor)
                self.closeDoors()
        self.state = "stand"
            
    def goDown(self, floorNum):
        self.closeDoors()
        self.state = "down"
        # continue going down until floor is reached
        while(self.currentFloor > floorNum):
            self.currentFloor -= 1
            # pause for five seconds if a floor we're passing has a request
            if(self.currentFloor in self.requests):
                self.openDoors()
                time.sleep(5)
                self.closeDoors()
                self.requests.remove(self.currentFloor)
        self.state = "stand"

    def openDoors(self):
        self.doors = "open"

    def closeDoors(self):
        self.doors = "closed"
        

class Scheduler:
    def __init__(self):
        self.requestBank = []
        # populate elevators
        self.elevators = []
        for i in range(0, 3):
            self.elevators.append(Elevator())

    def getStandingOnCurrentFloor(self, floorNum):
        for elevator in self.elevators:
            if(elevator.state == 'stand' and elevator.currentFloor == floorNum):
                return elevator
        return None

    def getElevatorMovingToCurrentFloor(self, floorNum):
        for elevator in self.elevators:
            if(elevator.currentFloor > floorNum and elevator.state == 'down'):
                return elevator
            elif(elevator.currentFloor < floorNum and elevator.state == 'up'):
                return elevator
        return None

    def getAnyStandingElevator(self):
        for elevator in self.elevators:
            if(elevator.state == 'stand'):
                return elevator
        return None

    def requestElevator(self, floorNum):
        # find appropriate elevator
        if(self.getStandingOnCurrentFloor()):
            elevator = self.getStandingOnCurrentFloor()
        elif(self.getElevatorMovingToCurrentFloor()):
            elevator = self.getElevatorMovingToCurrentFloor()
        elif(self.getAnyStandingElevator()):
            elevator = self.getAnyStandingElevator()

        # make request
        elevator.requestFloor(floorNum)
    
if(__name__ == "__main__"):
    scheduler = Scheduler()