Question

I tried to write a code that would add the position of a lists element to a new list. When I later on would try to add a new element to the original list from a different object, the placement of the object would be compared with the list where I saved my previous element to make sure it doesn’t get replaced.

I’ll paste the part of the code that is relevant to my question and it looks like this:

class gamefield:
def __init__(self):

    self.table= [ [ "0" for i in range(10) ] for j in range(10) ]

class snake:
def __init__(self,sign):
    self.sign = sign
    self.x = random.randint(1,9) 
    self.y = random.randint(1,9)    
    self.bodylist = []
    gamefield.table[self.x][self.y] = sign
    self.bodylist.append(gamefield.table.index(sign))

field = gamefield()  

snake1 = snake("+")

But I get the error:
“”self.bodylist.append(gamefield.table.index(sign))
ValueError: ‘+’ is not in list””

Shouldn’t the ‘+” be in the list since I add it to gamefield.table just before I execute the code that causes the error?

Answer 1

It’s not in the list table, it’s in the list table[x]. Your table is a list of lists, like so:

[
  ["0", ... ,"0"],
  ["0", ... ,"0"],
  ..
  ..
  ["0", ... ,"0"]
]

You probably should add the tuple (x,y) to the body list