Filter nested list python

Question

a=[[(1,2),(7,-5),(7,4)],[(5,6),(7,2)],[(8,2),(20,7),(1,4)]]

A nested list of coordinates are as given in a.

For example (1,2) refers to x,y coordinates.

Imposing condition that x,y> 0 & <10 and deleting those points.

for x in a:
    for y in x:
        for point in y:
            if point<=0 or point>=10:
                a.remove(x)

Expected result a=[[(5,6),(7,2)]] This is the error I get:

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

That error message doesn't match that code; that's a numpy error message, and you have no use of numpy arrays in that code. — DSM
– DSM, Commented Apr 23, 2015 at 13:28

mhawke · Accepted Answer · 2015-04-23 13:38:36Z

3

Try this list comprehesion.

>>> a = [[(1,2),(7,-5),(7,4)], [(5,6),(7,2)], [(8,2),(20,7),(1,4)]]
>>> [l for l in a if all((0<x<10 and 0<y<10) for x,y in l)]
[[(5, 6), (7, 2)]]

answered Apr 23, 2015 at 13:38

mhawke

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EvenLisle · Accepted Answer · 2015-04-23 13:40:06Z

1

The following snippet will print [[(5, 6), (7, 2)]]:

a=[[(1,2),(7,-5),(7,4)],[(5,6),(7,2)],[(8,2),(20,7),(1,4)]]

def f(sub):
  return all(map(lambda (x,y): (0 < x < 10 and 0 < y < 10), sub))

a = filter(f, a)
print a

edited Apr 23, 2015 at 13:40

answered Apr 23, 2015 at 13:28

EvenLisle

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6 Comments

EvenLisle Over a year ago

I'm sorry, I hadn't read the question (or the input rather) carefully enough. I've updated my answer.

miradulo Over a year ago

Better now :) You can make your f function quite a bit shorter by having both sides of the range, for instance 0 < point[0] < 10

mhawke Over a year ago

That's still wrong. The output should be` [[(5,6),(7,2)]]` that being the only sublist for which all points meet the condition.

miradulo Over a year ago

@mhawke Nice catch, totally missed that in the question.

EvenLisle Over a year ago

Once again, i had not read the question carefully enough. Thanks, @mhawke, re-updated.

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