collision detection program won't work in Turtle

Question

When I run the program it freezes up and doesn't work. The point of the program is to print something out when the x and y position coordinates of the user controlled turtle which is controlled by key-bindings is less then 10 pixels from the other turtle x and y position coordinates.

import turtle
import random
wn = turtle.Screen()
wn.setup(width = 450, height = 450)
player = turtle.Turtle()
player2 = turtle.Turtle()

def up():

    y  = player.ycor()
    y = y + 5
    player.sety(y)
    if y>=310:
        player.sety(y-15)

def down():
    y = player.ycor()
    y = y - 5
    player.sety(y)
    if y<-310:
        player.sety(y+15)


def left():
    x = player.xcor()
    x = x - 5
    player.setx(x)
    if x<=-625:
        player.setx(x+15)


def right():
    x = player.xcor()
    x = x + 5
    player.setx(x)
    if x>=625:
        player.setx(x-15)

player.penup()
player.setpos(0,0)
player.showturtle()
player.shape("square")
wn.bgcolor("green")
player2.shape("square")
player2.penup()
player2.setpos(300,300)
player2.showturtle()

turtle.listen()
turtle.onkeypress(up,"Up")

turtle.onkeypress(left,"Left")

turtle.onkeypress(right,"Right")

turtle.onkeypress(down, "Down")


def checkcollision(player,player2):
        if abs(player.xcor() - player2.xcor()) < 10 and abs(player.ycor() - player2.ycor()) < 10:
            player.write("collision")


while True:
    checkcollision(player,player2)

Answer 1

I think it freezes because of the loop in your code:

while True:
    checkcollision(player,player2)

It's always checking the collision, move that code to the movement functions Up , Down , Left , Right etc and then call it after doing the movement.