There's a good discussion on the python mailing list regarding flatten: http://mail.python.org/pipermail/python-list/2005-July/330367.html
particularly, it's got a number of different implementations, and benchmarks. On Thu, 28 Jun 2007, Hamptonio wrote: > > I often want to flatten nested lists, and such a command (like > Mathematica's Flatten) does not seem to be present in sage. I propose > adding such a command into the misc.py. I am appending some candidate > code below, and I will also put it on sage-trac (http:// > www.sagemath.org:9002/sage_trac/ticket/395) > > Here's my function: > > def flatten(in_list, ltypes=(list, tuple)): > """ > Flattens a nested list. > > INPUT: > in_list -- a list or tuple > ltypes -- optional list of particular types to flatten > > OUTPUT: > a flat list of the entries of in_list > > EXAMPLES: > sage: flatten([[1,1],[1],2]) > [1, 1, 1, 2] > sage: flatten((['Hi',2,vector(QQ,[1,2,3])],(4,5,6))) > ['Hi', 2, (1, 2, 3), 4, 5, 6] > sage: flatten((['Hi',2,vector(QQ,[1,2,3])], > (4,5,6)),ltypes=(list, tuple, > sage.modules.vector_rational_dense.Vector_rational_dense)) > ['Hi', 2, 1, 2, 3, 4, 5, 6] > """ > index = 0 > new_list = [x for x in in_list] > while index < len(new_list): > if not new_list[index]: > new_list.pop(index) > continue > while isinstance(new_list[index], ltypes): > new_list[index : index + 1] = list(new_list[index]) > index += 1 > return new_list > > > > > --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://sage.scipy.org/sage/ and http://modular.math.washington.edu/sage/ -~----------~----~----~----~------~----~------~--~---
