closest

Example Python program closest.py

Modules

• import Tkinter as tk
• import time
• from operator import itemgetter
• from math import sqrt
• from random import randint
• from Queue import Queue
• from threading import Thread

Classes

• class App(object):

Methods

• def vdist(q, (x1,y1), (x2,y2)):
• def vclosest(q, points):
• def calc(q, points):
• def init(self, q, points, timeout=10):
• def draw_label(self):
• def draw_canvas(self):
• def draw_items(self):
• def draw_line(self, (x1,y1), (x2,y2)):
• def remove_line(self):
• def next_step(self):

Code

Python tkinter example

import Tkinter as tk
import time

from operator import itemgetter
from math import sqrt
from random import randint
from Queue import Queue
from threading import Thread

def vdist(q, (x1,y1), (x2,y2)):
    q.put(((x1,y1), (x2,y2)))
    return sqrt((x1-x2)**2 + (y1-y2)**2)

def vclosest(q, points):
    if len(points) == 1: return float("inf")
    if len(points) == 2: return vdist(q, *points)

    xs = sorted(points, key=itemgetter(0))
    ys = sorted(points, key=itemgetter(1))

    m = len(points)/2
    left = vclosest(q, xs[:m])
    right = vclosest(q, xs[m:])
    delta = min(left, right)

    q.put(("label", delta))

    for i in xrange(len(ys)):
        for j in range(1,8):
            if i+j < len(ys):
                d = vdist(q, ys[i], ys[i+j])
                delta = min(delta, d)
                q.put(("label", delta))

    return delta

def calc(q, points):
    d = vclosest(q, points)
    q.put(("final", d))

class App(object):
    line = None

    def __init__(self, q, points, timeout=10):
        self.queue = q
        self.points = points
        self.timeout = timeout

        # create TK root object
        self.root = tk.Tk()

        # draw all UI elements
        self.draw_label()
        self.draw_canvas()
        self.draw_items()
        self.next_step()

        # run tkinter mainloop
        self.root.mainloop()

    def draw_label(self):
        self.label = tk.Label(text="")
        self.label.pack()

    def draw_canvas(self):
        self.canvas = tk.Canvas(self.root, width=600, height=600)
        self.canvas.pack()

    def draw_items(self):
        for (x, y) in self.points:
            self.canvas.create_oval(x+49,y+49,x+51,y+51,fill="blue")

    def draw_line(self, (x1,y1), (x2,y2)):
        self.remove_line()
        self.line = self.canvas.create_line(x1+50,y1+50,x2+50,y2+50,fill="red")

    def remove_line(self):
        if self.line is not None:
            self.canvas.delete(self.line)

    def next_step(self):
        (p1, p2) = self.queue.get(timeout=500)
        if p1 == "label":
            self.label.configure(text=p2)
            self.root.after(self.timeout/10, self.next_step)
        elif p1 == "final":
            self.remove_line()
            self.label.configure(text=("Minimal distance is: %s" % p2))
        else:
            self.draw_line(p1, p2)
            self.root.after(self.timeout, self.next_step)


# generate random points
q = Queue()
points = [(randint(1,500), randint(1,500)) for _ in xrange(50)]

# separate thread to calculate closest points
Thread(target=calc, args=(q, points)).run()

# run Tkinter application
App(q, points).mainloop()

Useful Links

• Articles: https://python-commandments.org/
• Python shell: https://bsdnerds.org/learn-python/
• Tutorial: https://pythonprogramminglanguage.com/