Having just seen Raymond's talk on Beyond PEP-8 here: https://www.youtube.com/watch?v=wf-BqAjZb8M, it reminded me of my own recent post where I am soliciting opinions from non-newbies on the relative Pythonicity of different versions of a routine that has non-simple array manipulations.
The blog post: http://paddy3118.blogspot.co.uk/2015/04/pythonic-matrix-manipulation.html The first, (and original), code sample: def cholesky(A): L = [[0.0] * len(A) for _ in range(len(A))] for i in range(len(A)): for j in range(i+1): s = sum(L[i][k] * L[j][k] for k in range(j)) L[i][j] = sqrt(A[i][i] - s) if (i == j) else \ (1.0 / L[j][j] * (A[i][j] - s)) return L The second equivalent code sample: def cholesky2(A): L = [[0.0] * len(A) for _ in range(len(A))] for i, (Ai, Li) in enumerate(zip(A, L)): for j, Lj in enumerate(L[:i+1]): s = sum(Li[k] * Lj[k] for k in range(j)) Li[j] = sqrt(Ai[i] - s) if (i == j) else \ (1.0 / Lj[j] * (Ai[j] - s)) return L The third: def cholesky3(A): L = [[0.0] * len(A) for _ in range(len(A))] for i, (Ai, Li) in enumerate(zip(A, L)): for j, Lj in enumerate(L[:i]): #s = fsum(Li[k] * Lj[k] for k in range(j)) s = fsum(Lik * Ljk for Lik, Ljk in zip(Li, Lj[:j])) Li[j] = (1.0 / Lj[j] * (Ai[j] - s)) s = fsum(Lik * Lik for Lik in Li[:i]) Li[i] = sqrt(Ai[i] - s) return L My blog post gives a little more explanation, but I have yet to receive any comments on relative Pythonicity. -- https://mail.python.org/mailman/listinfo/python-list
