CODEWITHSUNDEEP
pythonpython-3.xturtle-graphics
eaglebrain
eaglebrain

Reputation: 88

Python turtle drawing updated for turtle.tracer(0,0)

I am a newbie using python 3.2.3

When I ran the module in the python IDLE, the turtle drew a square without any update on the screen, so the window appeared blank, and after I input any key, the turtle and the square appeared due to the call of turtle.update().

However, when I double-clicked the .py file storing the below code in my document and executed it directly, the square always showed up before I input any key.

The interesting part is that the turtle was not shown but only the square was shown.

It seems that there was a turtle update only for the square after drawing even if I had already set turtle tracer to (0,0).

Is this considered a bug and how can I solve it? Thanks for the help.

import turtle

def drawSquare():
    turtle.down();
    turtle.begin_fill();
    turtle.goto(10, 0);
    turtle.goto(10, 10);
    turtle.goto(0, 10);
    turtle.goto(0, 0);
    
    turtle.end_fill();
    turtle.up();

def tUpdate():
    turtle.update();

turtle.tracer(0,0);
drawSquare();
input("Not updated. Press any key.");
tUpdate();
print("Updated");
turtle.mainloop();

Upvotes: 2

Views: 10329

Answers (1)

cdlane
cdlane

Reputation: 41895

You've got a couple of things working against you: the poor documenation provided for tracer() and the fact that end_fill() and up() cause updates to occur. tracer() is not really meant to hide things from the user until you're ready to display them -- it's a speed optimization so that the user doesn't have to see every drawing step in a complicated image. You don't have full control over when updates will occur.

Here's a rework of your example that displays the behaviour you want at the cost of it no longer being a filled square. I've swapped your input() trigger for a mouse click on the window instead but your approach will work just as well here too:

from turtle import Turtle, Screen

def drawSquare(turtle):
    turtle.goto(100, 0)
    turtle.goto(100, 100)
    turtle.goto(0, 100)
    turtle.goto(0, 0)

screen = Screen()

screen.tracer(0, 0)

screen.onclick(lambda x, y: screen.update())

turtle = Turtle()

drawSquare(turtle)

screen.mainloop()

I also made which are turtle methods, and which are screen methods, more explicit. The beginning programmer friendly design of the turtle library tends to blur these in the interest of ease of use.

Upvotes: 3

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