Re: how to make a nested list

2011-09-15 Thread Chris Angelico
On Fri, Sep 16, 2011 at 8:02 AM, Vlastimil Brom wrote: > Besides the above sugestions to correct the nested list approach, > if you need to set and access the data at the given "coordinates" you > could also use a nested defaultdict... The defaultdict is efficient for a sparse matrix, but I suspe

Re: how to make a nested list

2011-09-15 Thread Vlastimil Brom
2011/9/15 Stef Mientki : > hello, > > I need a nested list, like this > A= [ [None,None], [None,None], [None, None] ] A[2][0] =77 A > [[None, None], [None, None], [77, None]] > ... > > thanks, > Stef > -- > http://mail.python.org/mailman/listinfo/python-list > Besides the above suge

Re: how to make a nested list

2011-09-15 Thread John Ladasky
Stef, Are your bottom-level lists always of length 2? If so, then you could use an array, instead of a list of lists. Python ships with a module called array, but it doesn't allow you to put non-numeric types into arrays, and it looks like you want the NoneType. I use the popular numpy module,

Re: how to make a nested list

2011-09-15 Thread Gary Herron
On 09/15/2011 09:57 AM, Stef Mientki wrote: hello, I need a nested list, like this >>> A= [ [None,None], [None,None], [None, None] ] >>> A[2][0] =77 >>> A [[None, None], [None, None], [77, None]] Because the list is much larger, I need a shortcut (ok I can use a for loop) So I tried >>> B =

Re: how to make a nested list

2011-09-15 Thread Peter Pearson
On Thu, 15 Sep 2011 18:57:24 +0200, Stef Mientki wrote: [snip] > Because the list is much larger, I need a shortcut (ok I can use a for loop) > So I tried > >>> B = 3 * [ [ None, None ]] > >>> B[2][0] = 77 > >>> B > [[77, None], [77, None], [77, None]] > > which doesn't work as expected. > > any su

RE: how to make a nested list

2011-09-15 Thread Prasad, Ramit
>>> B = 3 * [ [ None, None ]] That makes a list of the exact same list object: [ a, a, a ] where a = [ None, None ]. Instead I would do something like (untested python2.x): B = [ [ None, None ] for x in xrange(3) ] Ramit Ramit Prasad | JPMorgan Chase Investment Bank | Currencies Technology 712

how to make a nested list

2011-09-15 Thread Stef Mientki
hello, I need a nested list, like this >>> A= [ [None,None], [None,None], [None, None] ] >>> A[2][0] =77 >>> A [[None, None], [None, None], [77, None]] Because the list is much larger, I need a shortcut (ok I can use a for loop) So I tried >>> B = 3 * [ [ None, None ]] >>> B[2][0] = 77 >>> B [