Tanay Soni - 6 months ago 40

Python Question

I have two lists holding x and y co-ordinates of points where each corresponding element represents a point.

Just an example, X_List = [1, 3, 1, 4], Y_List = [6, 7, 6, 1] then points are (1,6) (3,7) (1,6) (4,1). Thus, the most common point is (1,6).

Here's my code:

`Points=[]`

for x,y in zip(X_List, Y_List):

Points.append([x,y])

MostCommonPoint = max(set(Points), key=Points.count)

But, this will not work work as

Answer

First, `zip`

returns a list of tuples (or an iterator of tuples in Python 3). That means you could just use `zip(X_List, Y_List)`

instead of `Points`

(or `list(zip(X_List, Y_List))`

on Python 3), and your code would work. However, it would take quadratic time.

A faster way is to use a `collections.Counter`

, which is a dict subclass designed for counting things:

```
import collections
# Produce a Counter mapping each point to how many times it appears.
counts = collections.Counter(zip(X_List, Y_List))
# Find the point with the highest count.
MostCommonPoint = max(counts, key=counts.get)
```