# Computing bounding box for a list of coordinates in Python

### Problem:

You have a list of X/Y coordinates, for example:

```coords = [(6.74219, -53.57835),
(6.74952, -53.57241),
(6.75652, -53.56289),
(6.74756, -53.56598),
(6.73462, -53.57518)]```

For these coordinates you want to compute the minimum bounding box. ### Solution 1 (no NumPy):

```class BoundingBox(object):
"""
A 2D bounding box
"""
def __init__(self, points):
if len(points) == 0:
raise ValueError("Can't compute bounding box of empty list")
self.minx, self.miny = float("inf"), float("inf")
self.maxx, self.maxy = float("-inf"), float("-inf")
for x, y in points:
# Set min coords
if x < self.minx:
self.minx = x
if y < self.miny:
self.miny = y
# Set max coords
if x > self.maxx:
self.maxx = x
elif y > self.maxy:
self.maxy = y
@property
def width(self):
return self.maxx - self.minx
@property
def height(self):
return self.maxy - self.miny
def __repr__(self):
return "BoundingBox({}, {}, {}, {})".format(
self.minx, self.maxx, self.miny, self.maxy)

# Usage example:
BoundingBox(coords)
# BoundingBox(6.73462, 6.75652, -53.57835, -53.56289)```

By using the `BoundingBox` class, you can directly access `bbox.width` and `bbox.height`. Although you can access the coordinates at `bbox, bbox, ...`,  you can avoid mixing up the coordinates by accessing them using `bbox.minx, bbox.maxx, bbox.miny and bbox.maxy`.

## Solution 2 (NumPy):

Using numpy makes managing a large amount of coordinates much more efficient. For this example, we’ll assume you stored the coordinates in a `(n,2)`-shaped array. For the example coordinates above, that’s easy:

```import numpy as np
coords = np.asarray(coords)```

We can use numpy’s builtin `min` and `max` functions to compute the min/max instead of writing them ourselves. You can have a look at  the source code, but for most applications it’s recommended to install UliEngineering and just use the code:

`sudo pip3 install git+https://github.com/ulikoehler/UliEngineering.git`

Example:

```from UliEngineering.Math.Coordinates import BoundingBox

# Usage example:
BoundingBox(coords)
# BoundingBox(6.73462, 6.75652, -53.57835, -53.56289)```

You can use this on a list of coordinates without explicitly converting them to a numpy array, because `min` and `max` will convert the list implicitly. However, this is inefficient, as it will be converted two times: Once in `min` and once in `max`.