looking for a neat solution to a nested loop problem

Mon Aug 6 14:29:31 EDT 2012

On 2012年08月06日, Grant Edwards <invalid at invalid.invalid> wrote:
> On 2012年08月06日, Tom P <werotizy at freent.dd> wrote:
>> On 08/06/2012 06:18 PM, Nobody wrote:
>>> On 2012年8月06日 17:52:31 +0200, Tom P wrote:
>>>>>>> consider a nested loop algorithm -
>>>>>>>> for i in range(100):
>>>> for j in range(100):
>>>> do_something(i,j)
>>>>>>>> Now, suppose I don't want to use i = 0 and j = 0 as initial values, but
>>>> some other values i = N and j = M, and I want to iterate through all
>>>> 10,000 values in sequence - is there a neat python-like way to this?
>>>>>> 	for i in range(N,N+100):
>>> 	 for j in range(M,M+100):
>>> 	 do_something(i,j)
>>>>>> Or did you mean something else?
>>>> no, I meant something else ..
>>>> j runs through range(M, 100) and then range(0,M), and i runs through 
>> range(N,100) and then range(0,N)
>> In 2.x:
>> for i in range(M,100)+range(0,M):
> for j in range(N,100)+range(0,N):
> do_something(i,j)
>> Dunno if that still works in 3.x. I doubt it, since I think in 3.x
> range returns an iterator, not?

Indeed it doesn't work in 3.x, but this does:
 from itertools import chain
 for i in chain(range(M,100),range(0,M)):
 for j in chain(range(N,100),range(0,N)):
 do_something(i,j)
-- 
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