Three by three

What this Python grid-manipulation question tests

This is a medium-difficulty Python question that probes your understanding of how nested data structures behave under assignment and mutation. It's the kind of problem that separates candidates who think carefully about object references from those who assume intuitive outcomes.

To solve it, you need to trace through code that builds or modifies a two-dimensional grid, paying close attention to whether you're creating independent copies or aliasing the same object across multiple cells. The question rewards careful mental execution and awareness of Python's reference semantics, especially when lists or mutable objects are involved in loops or initialization patterns.

• List references and shallow vs. deep copies
• Mutable object aliasing in nested structures
• Loop variable scope and object identity