CODEWITHSUNDEEP
python
manabreak
manabreak

Reputation: 5597

How to order a list of points by distance to a given point?

I have a list of items that have X and Y coordinates. Now, there's a method that takes X and Y parameters and should return a the list of coordinates ordered from the closest to the farthest based on the given parameters.

Basically, it looks something like this:

class Point:
    x = 0.0
    y = 0.0

# List of points
points = ...

def get_ordered_list(x, y):
    # return 'points' ordered by distance to (x,y)

I'm new to Python so I have pretty much no idea how to order the items. How would I do that?

Upvotes: 5

Views: 21166

Answers (4)

maxymoo
maxymoo

Reputation: 36555

You can pass a custom function to sort using the key parameter, for example to sort with the Euclidean norm like this:

def get_ordered_list(points, x, y):
   points.sort(key = lambda p: (p.x - x)**2 + (p.y - y)**2)
   return points

Upvotes: 13

mohan3d
mohan3d

Reputation: 245

You can use key in sorted function. 

class point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

 def distance(p1, p2):
     return ((p1.x - p2.x) ** 2 + (p1.y - p2.y) ** 2) ** 0.5

 sorted_points = sorted(points, key=lambda e: distance(e, target))

Upvotes: 2

zegkljan
zegkljan

Reputation: 8411

See the sort method of list, especially the key argument. It allows you to put a function which returns the key for sorting. So in your example it could be something like this:

def get_ordered_list(x, y):
    target_point = Point(x, y)
    points.sort(key=lambda p: distance(p, target_point))

assuming that distance(a, b) returns a distance between points a and b. Also note that sort() sorts the list in place, i.e. modifies the original list. If you want to return a new list which is sorted use the sorted function.

By the way - the class as you defined it is probably not going to work as you expect - the x and y fields are class fields. For them to be instance fields you have to define them in the constructor instead:

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

Upvotes: 1

Ayman
Ayman

Reputation: 11585

You need a function to get the distance between two points, I'll leave this function to you. It will return the distance between two points, one point will be your main point, the other from the list.

Use this function in the sorted method on the array of points.

Upvotes: 0

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