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# boards.py

Now make all Board instances iterable so we can loop through their cells attribute. If you need help, refer back to the Emulating Builtins video.

boards.py
```class Board:
def __init__(self, width, height):
self.width = width
self.height = height
self.cells = []
for y in range(self.height):
for x in range(self.width):
self.cells.append((x, y))

class TicTacToe(Board):
def __init__(self):
super().__init__(3, 3)
```

The challenge says to review "Emulating Builtins" but it is simply underlined and not linked. The actual link is https://teamtreehouse.com/library/emulating-builtins and @kennethlove explains it at the 5:05 mark in the video.

Since this challenge is a bit separated from the "Emulating Builtins" video, it was good to go back and watch the video to understand how this challenge is solved.

Moderator Edit: Best Answer selected for this post

Use yield from self.cells when you override the iter method.

just loop through, below works for me def iter(self): for item in self.cells: yield item

# code

class Board: def init(self, width, height): self.width = width self.height = height self.cells = [] for y in range(self.height): for x in range(self.width): self.cells.append((x, y))

```# Here is the code added
def __iter__(self):
for cell in self.cells:
yield cell
```

class TicTacToe(Board): def init(self): super().init(width = 3,height = 3)