Question

How to read line by line and parse from a file in python?

I am new to python.

The first line of input is the number of simulations.
The next line is the number of rows(x), followed by a single space, and followed by number of columns (y).
The next group of y lines will have x number of characters, with a single period (‘.’) representing a blank space and a single capitol “A” representing a starting Agent.

My code got an error

Traceback (most recent call last):
    numSims = int (line)
TypeError: int() argument must be a string or a number, not 'list'

Thanks for your help.

Input.txt

2   --- 2 simulations
3 3  -- 3*3 map
.A.  --map
AA.
A.A
2 2  --2*2 map
AA  --map
.A

def main(cls, args):
    numSims = 0
    path = os.path.expanduser('~/Desktop/input.txt') 
    f = open(path) 
    line = f.readlines() 
    numSims = int (line)
    print numSims
    k=0
    while k < numSims:
        minPerCycle = 1
        row = 0
        col = 0
        xyLine= f.readLines()
        row = int(xyLine.split()[0]) 
        col = int(xyLine.split()[1])
        myMap = [[Spot() for j in range(col)] for i in range(row)] 
        ## for-while
        i = 0
        while i < row:
            myLine = cls.br.readLines()
            ## for-while
            j = 0
            while j < col:
                if (myLine.charAt(j) == 'B'):
                    cls.myMap[i][j] = Spot(True)
                else:
                    cls.myMap[i][j] = Spot(False)
                j += 1
            i += 1

For Spot.py

Spot.py

class Spot(object):
isBunny = bool()
nextCycle = 0
UP = 0
RIGHT = 1
DOWN = 2
LEFT = 3
SLEEP = 4

def __init__(self, newIsBunny):
    self.isBunny = newIsBunny
    self.nextCycle = self.UP

Answer 1

Your errors are numerous, here are the ones I’ve found so far:

1. The line numSims = (int)line does not do what you think it does. Python does not have C casts, you need to call the int type instead:

   numSims = int(line)
   

   You compound this error later on by using an uppercase spelling of Int:

   row = (Int)(xyLine.split(" ")[0])
   col = (Int)(xyLine.split(" ")[1])
   

   Correct these in a similar manner:

   row = int(xyLine.split()[0])
   col = int(xyLine.split()[1])
   

   and since the default for .split() is to split on whitespace you can leave out the " " argument. Better yet, combine them into one line:

   row, col = map(int, xyLine.split())
   

2. You never increment k, so your while k < numSims: loop will continue forever, so you’ll get an EOF error. Use a for loop instead:

   for k in xrange(numSims):
   

   You don’t need to use while anywhere in this function, they can all be replaced with for variable in xrange(upperlimit): loops.

3. Python strings have no .charAt method. Use [index] instead:

   if myLine[j] == 'A':
   

   but since myLine[j] == 'A' is a boolean test, you can simplify your Spot() instantiation like so:

   for i in xrange(row):
       myLine = f.readLine()
       for j in xrange(col):
           cls.myMap[i][j] = Spot(myLine[j] == 'A')
   

4. There is no need to initialize variables quite so much in Python. You can get of most of the numSims = 0 and col = 0 lines, etc. if you are assigning a new value on a following line.

5. You create a ‘myMapvariable but then ignore it by referring tocls.myMap` instead.

6. There is no handling of multible maps here; the last map in the file would overwrite any preceding map.

Rewritten version:

def main(cls, args):
    with open(os.path.expanduser('~/Desktop/input.txt')) as f:
        numSims = int(f.readline())
        mapgrid = []
        for k in xrange(numSims):
            row, col = map(int, f.readline().split())  
            for i in xrange(row):
                myLine = f.readLine()
                mapgrid.append([])
                for j in xrange(col):
                    mapgrid[i].append(Spot(myLine[j] == 'A'))
         # store this map somewhere?
         cls.myMaps.append(mapgrid)