[Python-ideas] Python list of list matrixes without NumPy
apalala at gmail.com
Fri Apr 5 22:05:11 EDT 2019
The semantics of list operators are congruent, but unintuitive sometimes.
For example, I've fallen over this many times:
>>> 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:
>>> 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
>>> truth_matrix = lol(n, m, init=bool)
>>> 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).
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