Error - ValueError: invalid literal for int() with base 10: ' '

Question

I am making an online game using the sockets module and pygame in python.

def read_pos(str):
    if str is not None:
        string = str.split(",")
        return int(string[0]), int(string[1])
    else:
        pass

def make_pos(tup):
    return str(tup[0]) + "," + str(tup[1])


def redrawWindow(win,player, player2):
    win.fill((255,255,255))
    player.draw(win)
    player2.draw(win)
    pygame.display.update()


def main():
    run = True
    n = Network()
    startPos = read_pos(n.getPos())
    p = Player(startPos[0],startPos[1],100,100,(0,255,0))
    p2 = Player(0,0,100,100,(255,0,0))
    clock = pygame.time.Clock()

    while run:
        clock.tick(60)
        p2Pos = read_pos(n.send(make_pos((p.x, p.y))))
        p2.x = p2Pos[0]
        p2.y = p2Pos[1]
        p2.update()

This is the code I'm using in my client. in my server, the code is as follows

def convertPos(str):
    if str is not None:
        str = str.split(",")
        return int(str[0]), int(str[1])
    else:
        pass

def make_pos(tup):
    return str(tup[0]) + "," + str(tup[1])


pos = [(0,0),(100,100)]


def threaded_client(conn,player):
    conn.send(str.encode(make_pos(pos[player])))
    reply = " "
    while True:
        try:
            data = conn.recv(2048).decode()
            pos[player] = data

            if not data:
                print("Disconnected")
                break
            else:
                if player == 1:
                    reply = (pos[0])
                else:
                    reply = (pos[1])
                print("Received: ", data)
                print("Sending : ", reply)

            conn.sendall(str.encode(make_pos(reply)))
        except:
            break

    print("Lost connection")
    conn.close()

I am getting the error of ValueError: invalid literal for int() with base 10: ' '.

Can someone tell me why this is happening? The value of str in the function of convertPos() is coming in as a tuple which I am converting into a string and after that into an integer.

Answer 1

As you have converted it to string, the format you have is (x,y), you need to remove the brackets. You need to rewrite your convertPos function as:

def convertPos(str):
    if str is not None:
        str=str.strip("()")
        str = str.split(",")
        return int(str[0]), int(str[1])

EDIT You are not using the else part, so you can remove it.

And as @Azat Ibrakov says, you should not convert the tuple to an string, but if you need to do it, you can use ast.literal_eval like this:

import ast
def convertPos(str):
    return ast.literal_eval(str)

or use it directly in place of the convertPos function.

Answer 2

Obviously - as others have pointed out, the returned error is because you're trying to convert an empty string (or spaces) to an integer.

But the real issue is that the incoming co-ordinate is malformed. The code is not catching this error. You can write lots of code to determine what the error is, and report an accurate error. Or just plough-on as if everything is fine, but also catch any exception with a reasonable error message.

def convertPos(str):
    coord = None
    try:
        parts = str.split( ',', 2 )
        x = int( parts[0] )
        y = int( parts[1] )
        coord = ( x, y )
    except:
        raise ValueError( 'Malformed co-ordinate string [' + str.strip() + ']' )
    return coord

I suspect the socket code is not buffering a full packet, and maybe what's being processed is something like 122, , whereas the socket buffering needs to keep reading until a full co-ordinate has arrived.

So you could space-pad your co-ordinates to say a block of 11 characters - that way you know you must have received 11 characters to have a valid co-ordinate string. Alternatively use and end-of-coord marker, like a | , and then the socket code keeps buffing the input co-ordinate until that | arrives.