marsrover.py

###############################################################################
#   Filename: marsrover.py
#   Author:   Arunmozhi
#   Email:    [email protected]
#   Date:     29 May 2015
###############################################################################
import sys

class Rover:
    def __init__(self,pos):
        self.x = int(pos[0])
        self.y = int(pos[1])
        self.d = pos[2]
        self.directions = ['N','E', 'S', 'W']

    def turn_left(self):
        if self.directions.index(self.d) == 0:
            self.d = self.directions[3]
        else:
            self.d = self.directions[self.directions.index(self.d)-1]

    def turn_right(self):
        if self.directions.index(self.d) == 3:
            self.d = self.directions[0]
        else:
            self.d = self.directions[self.directions.index(self.d)+1]

    def move(self):
        if self.d == 'N':
            self.y += 1
        elif self.d == 'S':
            self.y -= 1
        elif self.d == 'E':
            self.x += 1
        else:
            self.x -= 1

    def follow_instructions(self, ins):
        steps = list(ins.strip())
        for step in steps:
            if step == 'L':
                self.turn_left()
            elif step == 'R':
                self.turn_right()
            elif step == 'M':
                self.move()

def run_rovers(filename):
    plat_x = 0
    plat_y = 0
    infile = open(filename, 'r')
    outfile = open("output.txt", 'w')
    parts = infile.readline().split()
    plat_x = int(parts[0])
    plat_y = int(parts[1])
    # create the first rover object so others can be iteratively overwritten
    rover = Rover(infile.readline().split())
    nextIsRover = False
    # read two lines at a time and plot rover positions
    for line in infile:
        if nextIsRover:
            rover = Rover(line.split())
            nextIsRover = False
        else:
            rover.follow_instructions(line)
            if 0 <= rover.x <= plat_x and 0 <= rover.y <= plat_y:
                outfile.write(" ".join([str(rover.x), str(rover.y), rover.d])+"\n")
            else:
                outfile.write("Sorry, this rover is off the plateau and lying in the valley :(\n")
            nextIsRover = True
    infile.close()
    outfile.write('============\n')
    outfile.close()

if __name__ == "__main__":
    if len(sys.argv) != 2:
        print "Usage: python marsrover.py <filename>"
    else:
        run_rovers(sys.argv[1])
        print "The current locations of mars rovers can be read from <output.txt>"