The semantics of list operators are congruent, but unintuitive sometimes. For example, I've fallen over this many times:

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truth_matrix = [[False] * n ] * m

It doesn't create what you'd want. The only safe way I know to creat an NxM matrix is:

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truth_matrix = [ [False for _ in range(n) for _ in range(m)]

There could be a library to deal with that common case, and those of checking if a list of lists (of lists?) is properly rectangular, square, etc., and several other common cases. It takes experience to be aware that `truth_matrix[i][j]` will change more than one "cell" if the initialization is the former. `numpy` is not part of stdlib. A standard library for list of list would be usefu, specially to newcomersl. I don't remember such being discussed lately.

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truth_matrix = lol(n, m, init=bool)

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other_matrix = lol(n, m, o, p, init=float)

Maybe it could also be done with syntax, but I don't have any ideas in that regard (I don't think "lol()" is overloaded). Regards, -- Juancarlo *Añez*