python turtle.onkey() in loop binding error

Question

I have been trying to bind number keys to change color turtle program, when i try to bind it in loop it only takes last color.

import turtle

colors = ('violet', 'indigo', 'blue', 'green', 'yellow', 'red', 'orange')
for i, c in enumerate(colors):
    turtle.onkey(lambda: turtle.color(c), i)

turtle.listen()
turtle.mainloop()

but works if I do it separately without loop

turtle.onkey(lambda: turtle.color(colors[1]), 1)
turtle.onkey(lambda: turtle.color(colors[2]), 2)
turtle.onkey(lambda: turtle.color(colors[3]), 3)

On running the program all i see is a blank window. Since I have not worked with turtle before could you elaborate what kind of output you're expecting while running the program — shuberman
– shuberman, Commented Aug 13, 2019 at 14:35

cdlane · Accepted Answer · 2019-08-13 20:07:42Z

1

I believe the problem is in how you setup your lambda:

from turtle import Screen, Turtle

COLORS = ('violet', 'indigo', 'blue', 'green', 'yellow', 'red', 'orange')

screen = Screen()

turtle = Turtle('turtle')
turtle.shapesize(4)  # big turtle in center of screen

for number, color in enumerate(COLORS):
    screen.onkey(lambda c=color: turtle.color(c), number)

screen.listen()
screen.mainloop()

I find that functools.partial sometimes makes this sort of thing less error-prone:

from turtle import Screen, Turtle
from functools import partial

COLORS = ('violet', 'indigo', 'blue', 'green', 'yellow', 'red', 'orange')

screen = Screen()

turtle = Turtle('turtle')
turtle.shapesize(4)  # big turtle in center of screen

for number, color in enumerate(COLORS):
    screen.onkey(partial(turtle.color, color), number)

screen.listen()
screen.mainloop()

answered Aug 13, 2019 at 20:07

cdlane

42.2k5 gold badges37 silver badges87 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

rho Over a year ago

it was obvious i couldn't see it "passing default value to lambda"! thanks a lot!

Collectives™ on Stack Overflow

python turtle.onkey() in loop binding error

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related