Re: Rewriting Recipe/410687 without map and lambda
On Dec 11, 8:29 pm, Terry Reedy [EMAIL PROTECTED] wrote: sofeng [EMAIL PROTECTED] wrote in message news:[EMAIL PROTECTED] |I would like to use the following recipe to transpose a list of lists | with different lengths.http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/410687 | | Here is an example of what I would like to do: | | Python 2.5.1 (r251:54863, May 18 2007, 16:56:43) | [GCC 3.4.4 (cygming special, gdc 0.12, using dmd 0.125)] on cygwin | Type help, copyright, credits or license for more information. | a = [[1,2,3],[4,5,6,7],[8,9]] | print map(lambda *row: list(row), *a) | [[1, 4, 8], [2, 5, 9], [3, 6, None], [None, 7, None]] | | | However, in the Python 3000 FAQ (http://www.artima.com/weblogs/ | viewpost.jsp?thread=211200), Guido says not to use map with lambda | because a list comprehension is clearer and faster. | | How can I rewrite the above recipe using a list comprehension instead? Here is the sort of thing Guido is talking about: a = [[1,2,3],[4,5,6,7],[8,9]] [list(r) for r in zip(*a)] [[1, 4, 8], [2, 5, 9]] Except in this case, zip does not pad, while map does, so the list comp form has to be [list(r) for r in map(None, *a)] [[1, 4, 8], [2, 5, 9], [3, 6, None], [None, 7, None]] but at this point, it is about as easy to put the lambda in place of None. But when one maps one sequence or equal-length sequences, Guido's point applies. tjr Thank you very much. -- http://mail.python.org/mailman/listinfo/python-list
Rewriting Recipe/410687 without map and lambda
I would like to use the following recipe to transpose a list of lists with different lengths. http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/410687 Here is an example of what I would like to do: Python 2.5.1 (r251:54863, May 18 2007, 16:56:43) [GCC 3.4.4 (cygming special, gdc 0.12, using dmd 0.125)] on cygwin Type help, copyright, credits or license for more information. a = [[1,2,3],[4,5,6,7],[8,9]] print map(lambda *row: list(row), *a) [[1, 4, 8], [2, 5, 9], [3, 6, None], [None, 7, None]] However, in the Python 3000 FAQ (http://www.artima.com/weblogs/ viewpost.jsp?thread=211200), Guido says not to use map with lambda because a list comprehension is clearer and faster. How can I rewrite the above recipe using a list comprehension instead? -sofeng -- http://mail.python.org/mailman/listinfo/python-list
Re: Parsing HTML
On Feb 8, 11:43 am, metaperl [EMAIL PROTECTED] wrote: On Feb 8, 2:38 pm, mtuller [EMAIL PROTECTED] wrote: I am trying to parse a webpage and extract information. BeautifulSoup is a great Python module for this purpose: http://www.crummy.com/software/BeautifulSoup/ Here's an article on screen scraping using it: http://iwiwdsmi.blogspot.com/2007/01/how-to-use-python-and-beautiful-... This article has moved to http://iwiwdsmp.blogspot.com/2007/02/how-to-use-python-and-beautiful-soup-to.html -- http://mail.python.org/mailman/listinfo/python-list
