On Fri, 28 Mar 2014 17:05:15 -0500, Mark H Harris wrote: > You might try this to flatten a list of lists:
We got that the first four times you posted it. No need for a fifth. > >>> from functools import reduce > >>> L = [[1,2,3],[4,5,6],[7],[8,9]] > >>> import operator as λ Why would you name the operator module the Greek letter l? Why not the Armenian letter Ւ (yiwn)? That's pure obfuscation. The operator module has nothing to do with "l", and nothing to do with Greek lambda. This is exactly the sort of foolish obfuscation that opponents warned about when Python first introduced support for non-ASCII identifiers. > >>> reduce(λ.add, L) > [1, 2, 3, 4, 5, 6, 7, 8, 9] Furthermore, this is a very inefficient way of flattening a nested list. Doubling the size of the list quadruples the time taken; increasing the size by a factor of 10 increases the time by a factor of more than 100: py> from operator import add py> from functools import reduce py> L = [[1]]*10000 py> with Stopwatch(): # code for this available on request ... x = reduce(add, L) ... time taken: 0.348851 seconds py> L = [[1]]*100000 py> with Stopwatch(): ... x = reduce(add, L) ... time taken: 41.344467 seconds -- Steven D'Aprano http://import-that.dreamwidth.org/ -- https://mail.python.org/mailman/listinfo/python-list
