I've been creating a game using Python, and in one of my functions,
def Enemy_Party(enemies, party):
def Sub_Fight(member, enemy, enemies, Prep):
Prep.destroy()
Fight(member, enemy, enemies)
for x in enemies:
Prep = Tk()
for y in party:
button = Button(Prep, text=y.name, command=Sub_Fight(y, x, enemies, Prep)).pack()
Prep.mainloop()
a single window is created, but with nothing in it. There is no error message, the blank window just sits there.
Yes, I have a function Fight, and it does take four arguments. Both 'enemies' and 'party' are defined as lists, and both have values within them (I've checked).
On that note, I have two questions: "Why does the program halt after creating one blank window?" and "Can you define windows in a 'For Loop'?
Let me know if you need any more code, and thanks ahead of time.
The program halts the first time mainloop is called, because that's what mainloop does -- it doesn't return until you destroy the window.
You have a fundamental misunderstanding of how to create windows. Every tkinter application needs a single instance of Tk. To create additional windows you need to create instances of Toplevel. You then need to call mainloop exactly once.
In your code, replace calls to Tk with calls to Toplevel, then remove the call to mainloop in your function. Presumably you're calling mainloop somewhere else in your code after all of the widgets have been created.
I notice that you're defining Tk() inside a for loop. Depending on how many times this loop iterates, you could be creating many instances of Tk() when actually you should never create more than one. I would advise creating your window outside of the loop and populating it as you need to using the loop (or whatever else you may decide to use).
Related
I would like to make a python tkinter window with custom-moving widgets on a canvas to simulate motion. For now, I have one canvas, and one not-moving oval widget. I am having problems at the base level; mainloop(). I understand that it runs in wait for the user to do something, but I am having a hard time seeing:
How to control/see exactly what code mainloop() is reiterating (where, and only tkinter?);
How to properly interrupt it and return to it from another function, if it doesn't do it itself;
What code should be reiterated? All tkinter objects, or only updating changing ones? Use some kind of update operation instead? Finally;
What is the functionality difference between tkinter.mainloop() and window.mainloop()? Perhaps the previous questions will answer.
I have minor experience with Swift, and started learning the very similar Python yesterday evening. I've tried probably hundred of mutations to my code, which currently is in the test stage. I have moved everything in and out of the apparent range of the mainloop, and even got several hundred tiny Python windows all over the screen. Everything does one of two things: it does nothing, or gives me an error. Since I don't know what is even running, or if it is running, I can't diagnose anything. My goal is simply to move a circle one hundred pixels repeatedly. I've scanned around for sources, but—it may be me—a clear one is scarce. I have my code here all marked up. This page is closest to what I am looking for: Move a ball inside Tkinter Canvas Widget (simple Arkanoid game). Everything appears to be under mainloop. So, everything is redrawn every pass? Here, unfortunately, is my whole script; I can't only show pieces. It, for some reason, only brings up a small window, not a full-screen one. (Edit: I seem to have lost the screen size code)
import tkinter
import time
# Initial values for circle's corners and start idicator ('b'):
x1 = 10
y1 = 10
x2 = 210
y2 = 210
b = 0
# Window ('window')
window = tkinter.Tk()
# Canvas ('area')
area = tkinter.Canvas(window, width=1368, height=650)
area.place(x=0, y=0)
# Ovals to be placed on 'area'
oval1 = area.create_oval(x1,y1,x2,y2,fill='#42befe')
oval2 = area.create_oval(100,10,300,210,fill='#d00000')
# Turns b to 1 to start shifting when 'butt' is pressed:
def startFunc():
b = 1
print('b = 1')
# My button to activate 'startFunc'
butt = tkinter.Button(window, text='Start movement', command=startFunc)
butt.pack()
# Adjusts the x and y coordinates when they are fed in:
def Shift(A, B, C, D):
print('Shift activated.')
window.after(1000)
print('Edit and return:')
A += 100
B += 100
C += 100
D += 100
return(A, B, C, D)
# Problems start about here: my Mainloop section;
# I have little idea how this is supposed to be.
while True:
if b == 1:
# Takes adjusted tuple
n = Shift(x1, y1, x2, y2)
print('Returned edited tuple.')
# Changes coordinates
x1 = n[0]
y1 = n[1]
x2 = n[2]
y2 = n[3]
print(f'{x1}, {y1}, {x2}, and {y2}')
# Reiterate moving oval
oval1 = area.create_oval(x1,y1,x2,y2,fill='#42befe')
#Does this re-run 'window' relations outside here, or only within the 'while'?
window.mainloop()
It ought to show a 1368 by 650 window, not a tiny one. The button does nothing but print, which means the final 'while' is not running, despite the mainloop. It want it to loop inside the 'while' line, which should adjust coordinates and move my blue circle. The iteration may NOT touch the initial values, or else it would reset them.
In effect, calling mainloop is the same as if you added this to your code instead of calling mainloop():
while the_program_is_running():
event = wait_for_event()
process_the_event(event)
As a rule of thumb, mainloop() should be called exactly once after the UI has initialized and you are ready for the user to start interacting with your program. When it exits, you typically won't have any code after it, and your program will exit.
How to control/see exactly what code mainloop() is reiterating (where, and only tkinter?);
I don't know what you mean by "reiterating". It doesn't run any code except it's own internal code. It simply waits for events, and then dispatches them to handlers.
How to properly interrupt it and return to it from another function, if it doesn't do it itself;
It's exceedingly rare to do this in a running program. Typically, calling mainloop is the last thing your program does before the user starts interacting with it, and as soon as it exits your program quits.
However, to answer the specific answer of how to interrupt it, you can call the quit method of the root window. That will cause the most recent call to mainloop() to return.
What code should be reiterated? All tkinter objects, or only updating changing ones? Use some kind of update operation instead?
That question is hard to answer because it doens't make much sense. When you call mainloop(), it will watch for all events on all tkinter objects.
What is the functionality difference between tkinter.mainloop() and window.mainloop()
They have exactly the same effect and behavior. Tkinter oddly chose to make mainloop available from any widget. The most common way to call it is from either the tkinter module itself, or from the root window.
My goal is simply to move a circle one hundred pixels repeatedly.
The normal way to do that is to create a function that moves it one hundred pixels. Then, that function (-- or a function that calls it -- can put itself on an event queue to be run in the future.
For example, the following code will move a canvas object 100 pixels every second until the program exits:
def move_object():
the_canvas.move(item_id, 100, 0)
the_canvas.after(1000, move_object)
When it is called, it will move the item 100 pixels to the right. Then, it will place a new call to itself on the event queue to be picked up and handled in approximately 1000 milliseconds.
There are many working examples of using after on this site, including the question you linked to in your question.
Everything appears to be under mainloop. So, everything is redrawn every pass?
No, not exactly. The only objects that are redrawn are things that need to be redrawn. Moving objects on a canvas, resizing a window, dragging another window over your window, etc, all place an event on the event queue that tells tkinter "this object needs to be redrawn". The processing of that event happens automatically by mainloop. If nothing is happening in your application, nothing gets redrawn by mainloop.
It ought to show a 1368 by 650 window, not a tiny one
That is because you haven't given the main window a size. You've given the canvas a size, but you're using place which won't cause the containing window to grow or shrink to fit. As a beginner, you should completely avoid place and instead use pack or grid, because pack and grid will both automatically size your window to fit everything inside.
While it's tempting to use place for its perceived simplicity, in reality it usually requires you to do a lot more work than if you used one of the other geometry managers, and it results in a GUI that isn't particularly responsive to change.
while True:
You should almost never do this in tkinter. Tkinter -- and almost all event based programs -- rely on a steady flow of events. When you have an infinite loop, it cannot process those events. You can put an explicit call to update the screen inside your loop, but that is inefficient and should be avoided. If you need to do something periodically, create a function that encapsulates the body of your loop, then use after to get mainloop to run it while it is processing events.
window.after(1000)
You should almost never use after this way without a second argument. This usage is functionally no different than calling time.sleep(1) in that it prevents mainloop from processing events. You should structure your code to allow for a steady stream of events to be processed by mainloop.
while True: ... window.mainloop()
You definitely need to avoid calling mainloop inside a loop. A well behaved tkinter program should call mainloop() exactly once.
This question is NOT a duplicate of this question: Why doesn't the .bind() method work with a frame widget in Tkinter?
As you can see, I set the focus to the current frame in my game_frame() method.
I'm writing a Chip-8 emulator in Python and using Tkinter for my GUI. The emulator is running, but I can't get Tkinter to recognize keypresses. Here is my code:
def game_frame(self):
self.screen = Frame(self.emulator_frame, width=640, height=320)
self.screen.focus_set()
self.canvas = Canvas(self.screen, width=640, height=320, bg="black")
self._root.bind("<KeyPress-A>", self.hello)
for key in self.CPU.KEY_MAP.keys():
print(key)
self.screen.bind(key, self.hello)
self.screen.pack()
self.canvas.pack()
def hello(self, event):
if event.keysym in self.CPU.KEY_MAP.keys():
self.CPU.keypad[self.CPU.KEY_MAP[event.keysym]] = 1
self.CPU.key_pressed = True
self.CPU.pc += 2
sys.exit()
def run_game(self, event):
self.game_frame()
self.CPU.load_rom("TANK")
while True:
self._root.update()
self.after(0, self.CPU.emulate_cycle)
Could you please help me figure out what's going wrong? I think it might have something to do with my game loop interfering with the key bindings, but I'm not sure. The hello method never gets called when I run the game because the program continues to run in an infinite loop and never exits, regardless of what key is pressed. Thank you!
The problem could be due to two things. Without seeing all your code it's impossible to say for sure.
For one, you are binding to a capital "A" rather than a lowercase "a" -- have you testing that the binding works or not when you press a capital A?
Also, you are using after and update incorrectly. You may be starving the event loop, preventing it from processing key presses. The right way to run a function periodically is to have a function that (re)schedules itself.
class CPU_Class():
...
def run_cycle(self):
self.emulate_cycle()
self._root.after(1, self.run_cycle)
Two things to note:
don't use after(0, ...) -- you need to give tkinter at least a ms or so to process other events.
the run_cycle function is responsible for running one cycle, and then scheduling the next cycle to run in the future.
Once you do that, you no longer need your while loop. You can simply call run_cycle once, and that will start the CPU running.
I've searched for a simple animation code with Tkinter but I've found very different examples and I can't understand the correct way to write an animation.
Here my working code to display a simple moving circle:
import tkinter as tk
import time
root=tk.Tk()
canvas=tk.Canvas(root,width=400,height=400)
canvas.pack()
circle=canvas.create_oval(50,50,80,80,outline="white",fill="blue")
def redraw():
canvas.after(100,redraw)
canvas.move(circle,5,5)
canvas.update()
canvas.after(100,redraw)
root.mainloop()
In this code I can't correctly understand: how the after method works, where correctly put the update and the move method (before after method ?), is there another way to write an animation code? may you post me another example and comment the code please?
Thanks :)
Calling update
You should not call canvas.update(). As a general rule of thumb you should never call update. For a short essay on why, see this essay written by one of the original developers of the underlying tcl interpreter.
If you take out the call to canvas.update(), you have the proper way to do animation in a tkinter program.
Calling after to start the animation
You don't need to call after immediately before calling root.mainloop(). This works just as well:
...
redraw()
root.mainloop()
The choice to use or not use after in this specific case is dependent on if you want the animation to start immediately (possibly even before the widget is visible) or if you want it to happen after a short delay (possibly after the widget is made visible)
How after works
mainloop is nothing more than an infinite loop that checks the event queue for events. When it finds an event, it pops it off of the list and processes it. after is nothing more than making a request that says "in 100 ms, please add a new event to the queue". When the time limit expires, an event is added to the queue that says, in effect, "run this command". The next time the loop checks for events, it sees this event, pulls it off of the queue, and runs the command.
When you call after from within a method that itself was called by after, you're saying in effect "wait 100ms and do it again", creating an infinite loop. If you put the call to after before moving the object, you're saying "every 100ms run this function". If you put it after you're saying "run this function 100 ms after the last time it was run". The difference is very subtle and usually not perceptible unless your function takes a long time to run.
my code is:
from tkinter import *
import time
tk = Tk()
płótno = Canvas(tk, width=500, height=500)
płótno.pack()
płótno.create_polygon(10,10,10,70,70,10,fill="blue",outline="black")
for x in range(0,51):
płótno.move(1,5,0)
płótno.update()
rest(0.05)
płótno means canvas
I wrote a modified program of the 'mines' game, and I hope it shows every step/click graphically. I use time.sleep(0.5) to make a pause. So, in general the main program is like:
check_block():
if mine == 0:
buttons[current].config(image = tile_clicked)
elif mine == 1:
buttons[current].config(image = tile[1])
...
while(1):
time.sleep(0.5)
check_block()
get_next()
if check_fail():
break
However, the buttons don't update every 0.5 second: they are all updated together when the game(loop) finishes.
I guess it's just like 'cout' in C++: if you don't flush they will get stacked. So, is there a method to get them updated step by step, or say, instantly?
Thanks!
In all GUI systems you have to allow the message loop to run so that Windowing events occur promptly. So do not use a while loop like this. Instead, create a method that calls check_block() and get_next() and use after to call that function after a delay. At the end of that function, you use after again to call the same function again so that this function is called every 0.5 second forever. The after function queues a timer event and then lets the message queue be processed. Once your timer event fires, the callback function is run which allows you to do things and keep the UI responsive.
You should never call sleep in a GUI program. This is because the GUI must be "awake" at all times so that it can service events (including internal events that cause the screen to update). Instead, leverage the already-running eventloop by using the after method to put events on the queue at regular intervals.
In your case, you would replace the while loop with something like:
def do_check():
check_block()
if not check_fail():
root.after(500, do_check)
# in your initialization code, start the loop by calling it directly:
do_check()
I don't know what your get_next function does, so I don't know if you need to call it periodically too. Probably not. I'm guessing it waits for the next button press, which you don't need to do with tkinter or most other GUI toolkits. Instead, you configure the button to call a function when clicked.
Regardless, the way to do the type of looping you want is to place events on the event queue at a regular interval.
The following code exhibits a problem I do not understand:
from Tkinter import *
root = Tk()
cheese_var = IntVar()
parrot_var = IntVar(value=1)
check_menu = Menu(tearoff=0)
check_menu.add_checkbutton(label="Cheese", variable=cheese_var)
check_menu.add_checkbutton(label="Parrot", variable=parrot_var)
count = 0
class Top():
def __init__(self):
global count
count += 1
self.tl = Toplevel(root)
Label(self.tl, text="Window " + str(count)).pack()
self.mb = Menubutton(self.tl, text="Push Me", bg='pink')
self.menu = Menu(self.mb, tearoff=0)
self.menu.add_cascade(label="Choices", menu=check_menu)
self.menu.add_command(label="New Window", command=new_top)
self.mb.config(menu=self.menu)
self.mb.pack()
def new_top():
Top()
Top()
root.mainloop()
The menu brought up by the menu button in the created top level window initially behaves as expected. Clicking on the New Window command there creates a new such window, which also behaves as expected. Indeed, as long as you keep creating new top level windows, everything continues to work as expected. However, once you delete (close) any one of those windows, then, in a subsequently created new window, the Choices cascade on the new menu is not functional. (It is still OK in the windows created before the closing of one.)
The situation in which I initially encountered this symptom was much more complex, but I was able to simplify it down to the above example which exhibits the issue. I have discovered that I can avoid the problem by having each instance of Top create its own check_menu as an attribute; but I do not understand why this should be necessary. Please point me the way if there is one to avoid the problem without such replication of a cascade menu used in multiple windows.
Unfortunately, I don't think it is possible to do what you want. I'll try to explain as best as I can.
When you first run the script, check_menu is created and works fine for the first window. As you create more windows, check_menu is simply shared between them. However, when you close one of them, check_menu (and everything under it) is destroyed. So, when you create a new window after that, check_menu no longer exists and it doesn't show.
However, the script doesn't throw an error because, for some reason, Tkinter allows you to assign menus to things that aren't menus. Believe it or not, none of the following code:
self.menu.add_cascade(label="Choices", menu=None)
self.menu.add_cascade(label="Choices", menu=1)
self.menu.add_cascade(label="Choices", menu="")
will break the script. Each line simply does nothing but create an empty cascade "Choices".
That is basically what is happening. After closing one window, check_menu and everything under it is destroyed. Yet, Tkinter doesn't throw an error but instead assigns a menu to something that is no longer a menu (as far as what it is assigning the menu to, I believe it is using the old instance of check_menu, which was destroyed).
To solve this problem, recreate check_menu and everything under it each time you call Top. In other words, put the code for check_menu (and its options) in the __init__ method of Top. That way, each time Top is called, check_menu will exist.
Hope this helps (and that I explained it sufficiently :)