We Keep Coding

Best practice for modifying a python (turtle) object inside a function

Inside functions, I learned somewhere to work on copies of the arguments, for example: list_arg --> t = list_arg[:]. It made sense, so I try to do it consistently.
Now I am going again through the basics of programming, with the help of Think Python 2nd Edition by Allen B. Downey. In chapter 4 - Case study: interface design, I have to draw polygons with the help of the turtle module
import turtle
def mysquare(length, turtle_obj):
t = turtle_obj
t.pd()
for i in range(4):
t.fd(length)
t.lt(90)
t.pu()
def main():
bob = turtle.Turtle()
mysquare(100, bob)
turtle.mainloop()
if __name__ == "__main__":
main()
In this case, bob and t refer to the same turtle object. If I forget to make it hold the pen up t.pu() in the mysquare function, bob will (potentially) keep drawing in the main function.
As much as I would like to keep the programming style of writing functions that don't change their parameters, I don't know if it makes any sense in this situation.
Is there a general way, best practice to handle such a situation?
Conceptually, does my issue have to do with a particular programming paradigm (object-oriented, functional), or a language style (pythonic way)?

We can correct for the pen state on the way out using turtle's isdown() method:
import turtle
def mysquare(length, turtle_obj):
if was_up := not turtle_obj.isdown():
turtle_obj.pendown()
for _ in range(4):
turtle_obj.forward(length)
turtle_obj.left(90)
if was_up:
turtle_obj.penup()
turtle.penup()
mysquare(50, turtle)
turtle.goto(100, 100)
mysquare(25, turtle)
turtle.done()
The calls to mysquare() will return the pen state to what it was when the function was called. Assigning turtle_obj to t achieves nothing.

How to understand the operation of this Python Sierpinski code?

I have found this code on this website, and I have a few questions about it. I have already made a Sierpinski triangle on Python using my rudimentary knowledge and it is way too long and very bad.
I've done it using functions and some variables, but I have some questions with this code I have found. First of all, what is the "T" constantly brought up, the length and depth, and where is this all given a value. Where is the length and depth specified, and what does it do to the code?
Please note I am a beginner.
Here is the code:
import turtle
def draw_sierpinski(length,depth):
if depth==0:
for i in range(0,3):
t.fd(length)
t.left(120)
else:
draw_sierpinski(length/2,depth-1)
t.fd(length/2)
draw_sierpinski(length/2,depth-1)
t.bk(length/2)
t.left(60)
t.fd(length/2)
t.right(60)
draw_sierpinski(length/2,depth-1)
t.left(60)
t.bk(length/2)
t.right(60)
window = turtle.Screen()
t = turtle.Turtle()
draw_sierpinski(100,2)
window.exitonclick()

t = turtle.Turtle()
t is an instance of the class Turtle located in the module turtle that is previously imported
import turtle
As the instance t is in the global scope the python interpreter is able to find it, even within the function draw_sierpinski(length,depth)
I have no idea where you obtained the code however here are the docs for the turtle module.
To find out what the code does try it by yourself. Just pip install turtle and run the code
From the turtle docs
Turtle graphics is a popular way for introducing programming to kids.
It was part of the original Logo programming language developed by
Wally Feurzig and Seymour Papert in 1966. Imagine a robotic turtle
starting at (0, 0) in the x-y plane. After an import turtle, give it
the command turtle.forward(15), and it moves (on-screen!) 15 pixels in
the direction it is facing, drawing a line as it moves. Give it the
command turtle.right(25), and it rotates in-place 25 degrees
clockwise.

Why is Repl.it python turtle.tracer(n) limited to 150?

I'm making a recursive drawing of a tree using repl.it py turtle. This is my code
import turtle
import random
def about(x): return x * random.uniform(0.95,1.05)
# recursively draw a tree
def tree(t,a,s):
if s<2: return
t.left(a)
t.fd(s)
tree(t.clone(),about(30), s * about(.7))
tree(t,about(-30), s * about(.7))
t = turtle.getpen()
t.ht(); t.speed(0); t.tracer(0)
tree(t,90,40)
t.update()
Also here. But it only draws part of the tree. If I change it to
t.tracer(150)
then it works! Also tracer(10) works, but tracer(200) does not work. Is there a limit to how high tracer can go?

First, let's discuss your drawing code. Your tree consists of about 500 lines drawn by 500 different turtles! This seems excessive, so let's rewrite your code to use a single turtle that undoes it's movements rather clone itself:
from turtle import Screen, Turtle
from random import uniform
def about(x):
return x * uniform(0.95, 1.05)
# recursively draw a tree
def tree(t, a, s):
if s < 2:
return
t.forward(s)
t.left(a)
tree(t, about(30), s * about(0.7))
t.right(2 * a)
tree(t, about(-30), s * about(0.7))
t.left(a)
t.backward(s)
screen = Screen()
screen.tracer(0)
turtle = Turtle()
turtle.hideturtle()
turtle.setheading(90)
tree(turtle, 15, 50)
screen.tracer(1)
screen.mainloop()
As far as tracer() is concerned, I wasn't able to reproduce your results but the image never completed either. The argument to tracer() specifies that you only want to update the image on every nth graphic operation. This is very specialized and I only recommend values of 0 and 1. First, it's difficult to calculate what every nth update should be, based on the algorithm, and what makes sense visually to the user. Second, in standard Python turtle, there are some operations that cause an update regardless of tracer() setting which throws off this calculation, unless you know when these extra update occur.
In your case, for speed purposes, set tracer(0) when the intense drawing begins, and set tracer(1) when you're done drawing. Then everything should work fine.

trying to draw over sprite or change picture pyglet

I am trying to learn pyglet and practice some python coding with a questionnaire thing, but I am unable to find a way to make the background picture be removed or drawn on top of or something for 10 seconds. I am new and am lacking in a lot of the knowledge I would need, thank you for helping!
import pyglet
from pyglet.window import Window
from pyglet.window import key
from pyglet import image
import time
card1 = False
cat_image = pyglet.image.load("cat.png")
dog_image = pyglet.image.load("dog.png")
image = pyglet.image.load("backg.png")
background_sprite = pyglet.sprite.Sprite(image)
cat = pyglet.sprite.Sprite(cat_image)
dog = pyglet.sprite.Sprite(dog_image)
window = pyglet.window.Window(638, 404, "Life")
mouse_pos_x = 0
mouse_pos_y = 0
catmeme = pyglet.image.load("catmeme.png")
sprite_catmeme = pyglet.sprite.Sprite(catmeme)
#window.event
def on_draw():
window.clear()
background_sprite.draw()
card_draw1(63, 192, 385, 192)
def card1():
while time.time() < (time.time() + 10):
window.clear()
sprite_catmeme.draw()
#window.event
def card_draw1(x1, y1, x2, y2):
cat.set_position(x1, y1)
dog.set_position(x2, y2)
cat.draw()
dog.draw()
def card_draw2():
pass
#window.event
def on_mouse_press(x, y, button, modifiers):
if x > cat.x and x < (cat.x + cat.width):
if y > cat.y and y < (cat.y + cat.height):
card1()
game = True
while game:
on_draw()
pyglet.app.run()

There's a few flaws in the order and in which you do things.
I will try my best to describe them and give you a piece of code that might work better for what your need is.
I also think your description of the problem is a bit of an XY Problem which is quite common when asking for help on complex matters where you think you're close to a solution, so you're asking for help on the solution you've come up with and not the problem.
I'm assuming you want to show a "Splash screen" for 10 seconds, which happens to be your background? And then present the cat.png and dog.png ontop of it, correct?
If that's the case, here's where you probably need to change things in order for it to work:
The draw() function
It doesn't really update the screen much, it simply adds things to the graphical memory. What updates the screen is you or something telling the graphics library that you're done adding things to the screen and it's time to update everything you've .draw()'n. So the last thing you need in the loop would be window.flip() in order for the things you've drawn to actually show.
Your things might show if you try to wiggle the window around, it should trigger a re-draw of the scene because of how the internal mechanics of pyglet work..
If you don't call .flip() - odds are probable that the redraw() call will never occur - which again, is a internal mechanism of Pyglet/GL that tells the graphics card that something has been updated, we're done updating and it's time to redraw the scene.
a scene
This is the word most commonly used for what the user is seeing.
I'll probably throw this around a lot in my text, so it's good to know that this is what the user is seeing, not what you've .draw()'n or what's been deleted, it's the last current rendering of the graphics card to the monitor.
But because of how graphical buffers work we've might have removed or added content to the memory without actually drawing it yet. Keep this in mind.
The pyglet.app.run() call
This is a never ending loop in itself, so having that in a while game: loop doesn't really make sense because .run() will "hang" your entire application, any code you want to execute needs to be in def on_draw or an event that is generated from within the graphical code itself.
To better understand this, have a look at my code, i've pasted it around a couple of times here on SO over the years and it's a basic model of two custom classes that inherits the behavior of Pyglet but lets you design your own classes to behave slightly differently.
And most of the functionality is under on_??? functions, which is almost always a function used to catch Events. Pyglet has a lot of these built in, and we're going to override them with our own (but the names must be the same)
import pyglet
from pyglet.gl import *
key = pyglet.window.key
class CustomSprite(pyglet.sprite.Sprite):
def __init__(self, texture_file, x=0, y=0):
## Must load the texture as a image resource before initializing class:Sprite()
self.texture = pyglet.image.load(texture_file)
super(CustomSprite, self).__init__(self.texture)
self.x = x
self.y = y
def _draw(self):
self.draw()
class MainScreen(pyglet.window.Window):
def __init__ (self):
super(MainScreen, self).__init__(800, 600, fullscreen = False)
self.x, self.y = 0, 0
self.bg = CustomSprite('bg.jpg')
self.sprites = {}
self.alive = 1
def on_draw(self):
self.render()
def on_close(self):
self.alive = 0
def on_key_press(self, symbol, modifiers):
if symbol == key.ESCAPE: # [ESC]
self.alive = 0
elif symbol == key.C:
print('Rendering cat')
self.sprites['cat'] = CustomSprite('cat.png', x=10, y=10)
elif symbol == key.D:
self.sprites['dog'] = CustomSprite('dog.png', x=100, y=100)
def render(self):
self.clear()
self.bg.draw()
for sprite_name, sprite_obj in self.sprites.items():
sprite_obj._draw()
self.flip()
def run(self):
while self.alive == 1:
self.render()
# -----------> This is key <----------
# This is what replaces pyglet.app.run()
# but is required for the GUI to not freeze
#
event = self.dispatch_events()
x = MainScreen()
x.run()
Now, this code is kept simple on purpose, the full code I usually paste on SO can be found at Torxed/PygletGui, the gui.py is where most of this comes from and it's the main loop.
What I do here is simply replace the Decorators by using "actual" functions inside a class. The class itself inherits the functions from a traditional pyglet.window.Window, and as soon as you name the functions the same as the inherited onces, you replace the core functionality of Window() with whatever you decide.. In this case, i mimic the same functions but add a few of my own.
on_key_press
One such example is on_key_press(), which normally just contain a pass call and does nothing, here, we check if key.C is pressed, and if so - we add a item to self.sprites.. self.sprites just so happen to be in our render() loop, anything in there will be rendered ontop of a background.
Here's the pictures I used:
(named bg.jpg, cat.png, dog.png - note the different file endings)
class:CustomSprite
CustomSprite is a very simple class designed to make your life easier at this point, nothing else. It's very limited in functionality but the little it do is awesome.
It's soul purpose is to take a file name, load it as an image and you can treat the object like a traditional pyglet.sprite.Sprite, meaning you can move it around and manipulate it in many ways.
It saves a few lines of code having to load all the images you need and as you can see in gui_classes_generic.py you can add a heap of functions that's "invisible" and normally not readily availbale to a normal sprite class.
I use this a bunch! But the code gets complicated real fast so I kept this post simple on purpose.
the flip function
Even in my class, I still need to use flip() in order to update the contents of the screen. This is because .clear() clears the window as you would expect, that also triggers a redraw of the scene.
bg.draw() might in some cases trigger a redraw if the data is big enough or if something else happens, for instance you move the window.
but calling .flip() will tell the GL backend to force a redraw.
Further optimizations
There's a thing called batched rendering, basically the graphic card is designed to take enormous ammounts of data and render it in one go, so calling .draw() on several items will only clog the CPU before the GPU even gets a chance to shine. Read more about Batched rendering and graphics! It will save you a lot of frame rates.
Another thing is to keep as little functionality as possible in the render() loop and use the event triggers as your main source of coding style.
Pyglet does a good job of being fast, especially if you only do things on event driven tasks.
Try to avoid timers, but if you really do need to use time for things, such as removing cat.png after a certain ammount of time, use the clock/time event to call a function that removes the cat. Do not try to use your own t = time() style of code unless you know where you're putting it and why. There's a good timer, I rarely use it.. But you should if you're starting off.
This has been one hell of a wall of text, I hope it educated you some what in the life of graphics and stuff. Keep going, it's a hurdle to get into this kind of stuff but it's quite rewarding once you've mastered it (I still haven't) :)

Python and Pygame: Avoiding creating display surface twice

Heyo, this is a bit of an extension of the "Imports within imports" question asked earlier by me, so moderators feel free to merge the 2.
I have 2 files: A.py and B.py
#A.py
import pygame
import B
pygame.init()
tv = pygame.display.set_mode((256, 256))
tv.blit(<some surface here>)
#B.py
import pygame
pygame.init()
tv.blit()??? <--- I need to blit to tv, but how do I do it here?
I've tried making a blank file called Globe and assigning global values to it, but most of the time I've found it just makes my code look clunky and hard to write.
As well.. I don't want to init pygame twice either.
Is there any 'Pythonic' way to do it?

This question could really apply to any structured python application.
An executable python script is going to have an entry-point. This is the script that you call to start the application. Within this script, it can import library modules to reuse extended functionality.
Your application needs to have a single entry point. Lets assume it will be A.py.
B.py would be a library module that you will import and use its functions. It should not have to expect a global tv variable to operate on. Instead, it should have, at the very least, functions that take arguments. Or even, a class that is instantiated with a surface to use. The benefit of this approach is that your B module is now reusable and not dependent on some executable main script providing a global surface always called tv
B.py
def blitSpecial(surf):
surf.blit()
A.py
import B
tv = pygame.display.set_mode((256, 256))
B.blitSpecial(tv)
This is a good habit to get into. If all your modules depend on global objects from a main script, they will be far less reusable.
Specifically for your pygame situation, everything with the screen surface should be happening in A.py which is using all of the other modules for custom classes and utility functions.

You can write functions that take pygame.Surface objects as parameters:
class TV():
def __init__(self):
self.img = ...
### insert code to load image here
self.rect = self.img.get_rect()
def draw(self, surface):
surface.blit(self.img, self.rect.topleft)
def erase(self, surface, background):
surface.blit(background, self.rect)
I don't personally know how fast/slow this is compared to other sprite-based engines, but it's a very quick way to build out a class that can draw/erase itself.
To use it, just create a display screen and a TV object.
screen = pygame.display.set_mode((256, 256))
background = pygame.Surface((0,0),(256,256))
background.fill(pygame.Color(0,0,0))
screen.fill(pygame.Color(0,0,0))
myTVobj = TV()
Every time you want to draw a copy of the TV onto the screen you call
myTVobj.draw(screen)
To erase the object, use
myTVobj.erase(screen, background)
Then you can do fun stuff later with objects created from the TV class, like stick them in a list.
tv_list = []
tv_list.append(myTVobj)
You can add a whole bunch of TVs to a list and draw all of them at the same time.
tv_list = []
tv_list.append(myTVobj)
tv_list.append(myTVobj)
tv_list.append(myTVobj)
for tv in tv_list:
tv.draw(screen)
Or you can erase them all just by changing one line
for tv in tv_list:
tv.erase(screen)
Finally, you can add one more function to your TV class that lets you move it around. If you treat the .rect member as a 'position marker', all you have to do is fiddle with its members (hehe) to change your object's onscreen update location.
def move(self, move_amount=(1,0):
self.rect.move_ip(move_amount[0], move_amount[1])

You only need to call pygame.init() once, so I think your code should look something like this:
#A.py
import pygame
import B
def setup():
pygame.init()
tv = pygame.display.set_mode((256, 256))
...
mysurface = ...
tv.blit(mysurface)
return tv
#B.py
import pygame
def mydraw(surface):
...
surface.blit()
# In whatever file you like :)
if __name__ == '__main__':
surface_A = B.setup() # Do this first
mydraw(surface_A)