Need help converting grid to string

Question

I want to converting a list to string for an assignment. I can convert 1 row, however my teacher wants us to convert 3 separate rows to make a grid for the game of life. I've tried a bunch of different iterations of my code and the closest I've gotten is printing the top row.

I've added what my teacher wants each line to do so it should be more explainable

def gridToString( grid ):
    
    # create an empty string    
    mystr = ' '

    # for each row in the grid, convert that row

    for row in grid:
        mystr += int(input(row))

        # for each cell in the row, convert the cell
        for cell in row:
            mystr += int(input(cell))
            # add symbol to the string for this cell
            #   symbol + for cells that hold a zero
            if cell == 0:
                 cell = '+'
            #   letter O for cells that are non-zero
            elif cell == 1:
                cell = 'O'
        # add a newline to the string at the end of the grid row
        print(mystr, '\n')
    # return the string representation of the grid
    return mystr
    

    
    lifeGrid = [[1,1,1],
            [0,0,0],
            [0,0,1]]


    # convert the grid to a string
    gridStr = gridToString( lifeGrid )

    # print the string!
    print( gridStr )
    print('')

Answer 1

There are several issues in your attempt:

• The function should not call input(), nor print(). The purpose of the function is to convert the matrix that is given as argument to a string and return that string. This operation does not involve any user input, nor output to the terminal. So remove all input() and output() calls.

• The empty string is '', not ' '.

• print(mystr, '\n') does not alter mystr. Do do what the comment above it says, you should do mystr += '\n'

• Both mystr += int(input(row)) and mystr += int(input(cell)) cannot work: the right hand side of these assignments must be strings, so calling int() (which returns an integer) is wrong.

• mystr += int(input(row)) is doing nothing useful. mystr will get the contents of the row in the loop that follows below this statement, so this statement should just be removed.

• mystr += int(input(cell)) should instead be mystr += str(cell), but see next point

• The code that changes cell is useless, as after that change there is nothing done with this new value:

          if cell == 0:
              cell = '+'
          elif cell == 1:
              cell = 'O'
  

  Moreover, if cell is not 0, then it is expected to be 1, so no need to check that with elif cell == 1 -- it is the only possibility left. So make this an else.

  So do:

          if cell == 0:
              mystr += '+'
          else:
              mystr += 'O'
  

  Or shorter, using cell as an index:

          mystr += '+O'[cell]
  

  and this replaces the earlier assignment to mystr.

With those points corrected, you would get this:

def gridToString(grid):
    # not a space, but a really emmpty string: 
    mystr = ''
    for row in grid:
        # don't ask for input and don't print
        for cell in row:
            # assign to mystr the character that corresponds to cell
            mystr += '+O'[cell]
        # add a newline to the string (don't print)
        mystr += '\n'
    return mystr

Now it will work. Your question didn't explain whether the string should have a \n at the very end. It might be only necessary between lines.

Note that it is more pythonic to do it as follows:

def gridToString(grid):
    return '\n'.join(
        ''.join('+O'[cell] for cell in row) 
        for row in grid
    )

Here I left out the final \n