Is there an easier way to express this list slicing?

Thomas Ploch Thomas.Ploch at gmx.net
Thu Nov 30 21:07:10 CET 2006


John Henry schrieb:
> If I have a list of say, 10 elements and I need to slice it into
> irregular size list, I would have to create a bunch of temporary
> variables and then regroup them afterwords, like:
> 
> # Just for illustration. Alist can be any existing 10 element list
> a_list=("",)*10
> (a,b,c1,c2,c3,d1,d2,d3,d4,d5)=a_list
> alist=(a,)
> blist=(b,)
> clist=(c1,c2,c3)
> dlist=(d2,d3,d4,d5)
> 
> That obviously work but do I *really* have to do that?
> 
> BTW: I know you can do:
> alist=a_list[0]
> blist=a_list[1]
> clist=a_list[2:5]
> dlist=a_list[5:]
> 
> but I don't see that it's any better.
> 
> Can I say something to the effect of:
> 
> (a,b,c[0:2],d[0:5])=a_list    # Obviously this won't work
> 
> ??
> 
> I am asking this because I have a section of code that contains *lots*
> of things like this.  It makes the code very unreadable.
> 
> Thanks,
> 

I had a little bit of fun while writing this:

itemList = (a,b,c1,c2,c3,d1,d2,d3,d4,d5) and
itemList2 = (a1,a2,a3,b,c,d1,d2,d3,d4,d5) the next time.

def getSlices(aCount, bCount, cCount, dCount, items):
    a,b,c,d = (items[0:aCount],
                items[aCount:aCount+bCount],
                items[aCount+bCount:aCount+bCount+cCount],
		item[aCount+bCount+cCount:aCount+bCount+cCount+dCount])
    return list(a),list(b),list(c),list(d)

>>>a,b,c,d = getSlices(1,1,3,5,itemList)
>>>print a,b,c,d
['a'] ['b'] ['c1', 'c2', 'c3'] ['d1', 'd2', 'd3', 'd4', 'd5']

>>>a,b,c,d = getSlices(3,1,1,0,itemList2)
>>>print a,b,c,d
['a1', 'a2', 'a3'] ['b'] ['c'] []

%-)

Thomas



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