recursively change values in list of lists

[Carson Farmer]

Dear list,

I'm sure this is a relatively trivial problem, but I have been unable
to find any good examples/explanations on how to do this, so here
goes:

I have multi-polygon object, which is simply a list of polygons, where
each polygon is a list of lines, where each line is a list of points.
What I would like to do, is change the x and y values of each point,
all the while keeping the structure of the lists intact.

So in the end, the only thing that should be changed is the values,
not the lists themselves... clear as mud?

Any hints, and/or suggestions are greatly appreciated,
Carson

[twyk]

I see no recursion in the problem as stated. Can a polygon contain
another polygon?

I can see that if you had ...

e_1 = [(0,0),(3,0)]
e_2 = [(3,0),(2,3)]
e_3 = [(2,3),(0,0)]
triangle_1 = [e_1,e_2,e_3]

w_1 = [triangle_1,]

.... you might want to make a copy of triangle_1 that was offset by
some amount and add it to w_1. Is that the idea?

[castironpi]

On Aug 24, 9:17*am, "Carson Farmer" <carson.far...@ gmail.comwrote:

Dear list,

I'm sure this is a relatively trivial problem, but I have been unable
to find any good examples/explanations on how to do this, so here
goes:

I have multi-polygon object, which is simply a list of polygons, where
each polygon is a list of lines, where each line is a list of points.
What I would like to do, is change the x and y values of each point,
all the while keeping the structure of the lists intact.

So in the end, the only thing that should be changed is the values,
not the lists themselves... clear as mud?

Any hints, and/or suggestions are greatly appreciated,

Carson

I think you would be looking at:

seq3= [[[0,1],[1,2]],[[3,4]]]
[ [ [ setitem( seq1, i0, seq0* 2 ) for i0, seq0 in enumerate( seq1 ) ]
for seq1 in seq2 ] for seq2 in seq3 ]

>>seq3= [[[0,1],[1,2]],[[3,4]]]
[ [ [ setitem( seq1, i0, seq0* 2 ) for i0, seq0 in enumerate( seq1 ) ] for seq1 in seq2 ] for seq2 in seq3 ]

[[[None, None], [None, None]], [[None, None]]]

>>seq3

[[[0, 2], [2, 4]], [[6, 8]]]

[mblume]

Am Sun, 24 Aug 2008 15:17:46 +0100 schrieb Carson Farmer:

Dear list,

I'm sure this is a relatively trivial problem, but I have been unable to
find any good examples/explanations on how to do this, so here goes:

I have multi-polygon object, which is simply a list of polygons, where
each polygon is a list of lines, where each line is a list of points.
What I would like to do, is change the x and y values of each point, all
the while keeping the structure of the lists intact.

So in the end, the only thing that should be changed is the values, not
the lists themselves... clear as mud?

Any hints, and/or suggestions are greatly appreciated,

I always do something along the lines of:

for (i,obj) in enumerate(list_ of_objects):
obj = do_something_to _obj(obj)
list_of_objects[i] = obj
HTH. YMMV.
Martin