sells_table

class Cells:
    def __init__(self):
        self.cells = {}

    def setItem(self, r, c, value):
        if r not in self.cells:
            self.cells[r] = {}
        self.cells[r][c] = value

    def getItem(self, r, c):
        if r not in self.cells:
            return None
        if c not in self.cells[r]:
            return None
        return self.cells[r][c]

    def getNumber(self, r, c):
        v = self.getItem(r, c)
        if v is None:
            return 0
        return v

    def getCells(self):
        return self.cells

    def setItemErrors(self, r, c, step, value):
        if r not in self.cells:
            self.cells[r] = {}
        if c not in self.cells[r]:
            self.cells[r][c] = {}
        self.cells[r][c][step] = value

    def getItemErrors(self, r, c, step):
        if r not in self.cells:
            return None
        if c not in self.cells[r]:
            return None
        if step not in self.cells[r][c]:
            return None
        return self.cells[r][c][step]