There is this question to discover existing types:
Getting Python Tkinter Object Type
However I've just developed tooltips (balloons) I've assigned to some buttons and would like to be able to recall all of them as a unique type. Also down the road I'd like to hand-craft canvas objects which will operate like pseudo buttons with <enter>, <leave>, <active>, <press> and <release> events. How might I declare a new object type for them?
If I understand your question correctly you want to check if an instance created is a instance of the custom class, it can be directly done using isinstance:
class CustomTooltip():
pass
cwidget = CustomTooltip()
btn = tk.Button(root)
print(isinstance(cwidget, CustomTooltip)) # True
print(isinstance(b, CustomTooltip)) # False
print(type(cwidget) == CustomTooltip) # Not recommended
It is recommended to use isinstance rather than type, from the docs:
The isinstance() built-in function is recommended for testing the type of an object, because it takes subclasses into account.
I did not quite get your 2nd question, also it is better to keep a single question focused around one main question rather than asking more than one question.
Object Oriented Programming is probably the solution.
If I want to create a "new type" of tkinter button I can sub-class it.
class MySpecialButton(tkinter.Button):
pass
This doesn't do anything special at the moment but will give it a unique type (If it have understood your interpretation correctly)
The following example from another one of my answers, creates a special button with custom behaviour for hovering over the button
class HoverButton(tk.Button):
def __init__(self, master, **kw):
tk.Button.__init__(self,master=master,**kw)
self.defaultBackground = self["background"]
self.bind("<Enter>", self.on_enter)
self.bind("<Leave>", self.on_leave)
def on_enter(self, e):
self['background'] = self['activebackground']
def on_leave(self, e):
self['background'] = self.defaultBackground
With regard to canvas object, You can obviously create classes for these too which can contain methods for moving/resizing the object. As to how to create custom events for these, you can use tag_bind(item, event=None, callback=None, add=None) to bind a call back to a canvas object. A quick example below
import tkinter as tk
class CanvasShape:
def __init__(self, canvas, callback = None):
self.canvas = canvas
self.id = canvas.create_oval(10,10,50,50,fill='blue')
self.canvas.tag_bind(self.id,'<Button-1>',callback)
def clicked(e):
print("You clicked on a shape")
root = tk.Tk()
c = tk.Canvas(root,width=200,height=200)
c.grid()
shape = CanvasShape(c,callback=clicked)
root.mainloop()
This will create a circle that when you click on it will fire an event that is received by the clicked function.
Related
How can I change an attribute on the object when the attribute is Frame? I want to change the color of the frame.
class MyFrame:
def __init__(self, bg_color)
self.window = tk.Frame(self.parent, bg=bg_color)
mainApp:
frame_obj = MyFrame("blue")
#want to change the color after the frame obj has been created
frame_obj.window.bg = "red" #this does not work
Tkinter is based on different progamming language, named tcl and thats why things seem a bit unpythonic here.
The tk.Frame object isnt a pure python object, rather its an wrapped object in a tcl interpreter and thats why you cant address the attributes you intuitivly think you can. You need to adress the attributes in a way the tcl interpreter is abel to handle and therefor methods are created like widget.configure.
To achive what you want with your current code, it would look like:
import tkinter as tk
root = tk.Tk()
class MyFrame():
def __init__(self, bg_color):
self.window = tk.Frame(width=500,height=500,bg=bg_color)
frame_obj = MyFrame('blue')
frame_obj.window.pack(fill=tk.BOTH)
frame_obj.window.configure(bg='yellow')
root.mainloop()
In addition, the proper way for an OOP approach for a frame would look like this:
class MyFrame(tk.Frame):
def __init__(self,master,**kwargs):
super().__init__(master)
self.configure(**kwargs)
frame_obj = MyFrame(root,width=500,height=500,bg='green')
frame_obj.pack(fill=tk.BOTH)
This way your class becomes a child of the tk.Frame object and you can adress it directly. The syntax self in this context refers directly to the tk.Frame object. Also it is good practice to use the format of
def __init__(self,master,**kwargs):
while its the same for the parent/tk.Frame. It has a single positional argument, named master and keywords arguments for the configuration of the Frame.
Please take a look at a tutorial for tkinter and for OOP. If you had you would know that. Please dont feel offended, but StackOverflow requiers a brief reasearch and that includes to read documentation and take tutorials.
Whilst working on a tkinter application (Tcl/Tk 8.6 and Python 3.9.2) I recently encountered an error that I was able to resolve, but I think the existence of the error highlights some gaps in my knowledge and potential weaknesses in my approach.
A reproducible example of the error is below - this code will not work and returns the error AttributeError: 'parent_class' object has no attribute 'first'.
from tkinter import *
from tkinter import ttk
class child_one(ttk.Frame):
def __init__(self, parent, **kwargs):
super().__init__(parent, **kwargs)
self.x = 10
def print_x(self):
print(self.x)
class child_two(ttk.Frame):
def __init__(self, parent, **kwargs):
super().__init__(parent, **kwargs)
self.b = ttk.Button(self, text='Button 1',
command=parent.first.print_x).grid()
class parent_class(ttk.Frame):
def __init__(self, parent, **kwargs):
super().__init__(parent, **kwargs)
self.grid()
self.second = child_two(self)
self.first = child_one(self)
self.first.grid()
self.second.grid()
if __name__ == '__main__':
root = Tk()
w = parent_class(root)
root.mainloop()
However the code will work if I reverse the order in which the instances of child_one and child_two are created i.e. replacing
self.second = child_two(self)
self.first = child_one(self)
with
self.first = child_one(self)
self.second = child_two(self)
in the definition of parent_class.
I'd really appreciate any explanations or link to resources to help me understand the program flow which causes this to happen - it appears to me that when I create w and get to the line self.second = child_two(self) Python is just looking at the part of the instance of parent_class which has already been created, and not the whole definition of the class.
Would this happen if this was not the first instance of parent_class to be created? Is it specific to tkinter? (I was only able to create a simple reproducible example with tkinter widgets, not with classes more generally.)
I suppose another solution would be to make print_x a (static?) method of parent_class? I also assume there's not enough detail here to definitively state if that (or alternative structures) would be preferable to facilitate interface between the components of my application, but would be interested to hear any suggestions for good practices in this space.
There's really no mystery here. If you do self.first = child_one(self) first, it defines self.first. When you then call child_two(self), it is able to access parent.first since it was previously created.
However, if you call child_two(self) first, at that point in time parent.first doesn't exist. Thus, when you do command=parent.first.print_x, parent.first doesn't exist.
it appears to me that when I create w and get to the line self.second = child_two(self) Python is just looking at the part of the instance of parent_class which has already been created
That is correct. You can't reference things that haven't been created yet.
Would this happen if this was not the first instance of parent_class to be created? Is it specific to tkinter?
I'm not quite sure what you're asking in the first part of that question. It will always happen if you try to reference any object attribute before that attribute has been created. And no, this isn't specific to tkinter. It's a fundamental aspect of the way that python works.
This is a good example of why it's generally best to create proper functions rather than using lambda. lambda is good when you need to pass arguments, but you don't need to do that in this case. Even then, a proper function is better than directly referencing some other object at the time the button is defined. An arguably better way would be to use a function so that self.parent.first doesn't need to be resolved until you actually click the button.
For example:
class child_two(ttk.Frame):
def __init__(self, parent, **kwargs):
super().__init__(parent, **kwargs)
self.parent = parent
self.b = ttk.Button(self, text='Button 1', command=self.print_x)
self.b.grid()
def print_x(self):
self.parent.first.print_x()
When you say "Python is just looking at the part of the instance of parent_class which has already been created, and not the whole definition of the class", you seem to be expecting python to have built a static description of your class before the program starts running.
Python does not work that way, it's a dynamic language. As Bryan just said, the first variable is created only when you assign to it for the first.
I've written a program and I'm learning about classes and thus, rewriting the code to take advantage of classes and objects.
My problem is if I create a tkinter widget "dropdown menu" from a class, I can not retrieve the get.state variable.
class ...:
def make_drop_menu(self,parent,drop_opts,drop='empty',state=''):
self.parent = parent
self.drop = drop
self.drop_opts = drop_opts
self.state = tk.StringVar()
self.state.set(self.drop_opts[0]) # sets default value on drop (drop down menu)
self.drop = OptionMenu(self.parent, self.state, *self.drop_opts) # completed drop
return self.drop
----------------
class main:
self.widget = self.var.make_drop_menu(self.obj_mainwindow.btm_frame, self.col_opts)
Added for clearity:
window = windowclass() #windowclass is the style for tkinter. Makes a tkwindow.
self.widget = self.windowclass.var.make_drop_Menu() #
I've left out some code to simplify. But my main problem is that I create a widget called self.widget which builds my drop down menu. However, I have NO idea how to get the state of the drop down.
Hopefully the code makes sense.
If your class is named MyClass, then to access the state variable you would use the instance of the class. In your case it appears that self.var is the instance of your class, so it would look something like this:
self.var = MyClass()
self.var.make_drop_menu(...)
...
print(self.var.state.get())
Made the make_drop_menu class independent of any other class object. That way I could make a drop menu, assign the parent tk window, and create a method for getting the state variable when called.
Thanks to Bryan Oakley for the help!
I'm having a simple tkinter two frame application with a Label, Entry and Button widget and I want to access a StringVar() of FrameOne with a Entry and Button of FrameTwo.
If have seen a lots of examples of code, but do not get how this is been done in my example below. Many programmers are using a controller. If I would use a controller, I end up from an error to another.
For example:
FirstFrame = FrameOne(mainWindow)`
TypeError: __init__() missing 1 required positional argument: 'controller'
Which I completely understand, because I do not pass anything into the new 'controller' class argument when calling the Frame class. But I do not know what I should pass into this to solve it. Perhaps it is also caused by the lack of knowledge of using class variables (any literature tips are welcome).
The same counts for the solution to inherit FrameOne into FrameTwo. I bump into the same amount of errors applying to my code.
Another thing is that many programmers have examples of two frames that are not visible at the same time, while in my example I have two frames underneath each other at the same time.
An different related issue that I have is, what if the label widget of FrameOne was a Text widget? How do I access the widget from FrameTwo.
I could make it work with globals, but I do not want to use such writing and I will keep the access widget problem anyhow.
Please find my code below:
import tkinter as tk
class AppWindow():
def __init__(self, master):
self.master = master
master.title("Test Application")
master.geometry("1060x680")
master.grid_propagate(False)
class FrameOne(tk.Frame):
def __init__(self, parent):
super().__init__()
self["borderwidth"]=5
self["relief"]="ridge"
self.LabelText = tk.StringVar()
self.LabelText.set("It is not working yet")
self.testlabel = tk.Label(self, textvariable=self.LabelText)
self.testlabel.grid(row=1, column=1)
class FrameTwo(tk.Frame):
def __init__(self, parent):
super().__init__()
self["borderwidth"]=5
self["relief"]="ridge"
self.testentry = tk.Entry(self)
self.testentry.insert("end", "This should be working")
self.testentry.grid(row=1,column=1)
self.testbutton = tk.Button(self, text="Test the label", command=self.updatelabel)
self.testbutton.grid(row=1,column=2)
def updatelabel(self):
FrameOne.LabelText.set(self.testentry.get()) #HOW TO FIX THIS CODE THE RIGHT WAY?
#Create a window as defined in the AppWindow class
mainWindow = AppWindow(tk.Tk())
#Create a Frame as defined in class FrameOne
FirstFrame = FrameOne(mainWindow)
FirstFrame.grid(row=0, column=0) #Positioning Frame on Window
#Create a Frame as defined in class FrameOne
SecondFrame = FrameTwo(mainWindow)
SecondFrame.grid(row=1, column=0) #Positioning Frame on Window
Like with any python object, you access an attribute of an object using a reference to the object.
In your case, updatelabel should look like this:
def updatelabel(self):
FirstFrame.LabelText.set(self.testentry.get())
Note: your use of uppercase characters for instance variables makes your code much harder to comprehend. I recommend following the naming guidelines in PEP8.
i've recently come across a problem thats bugging me with the tkinter entry .get() function, I have put together an example code so you can see what i'm trying to do, I have two classes, a class for each window. In the first window(main window) I have an entry box, in the second window I am attempting to get the entry box text from the first window.
Here's the code: (Trying to get entry box info from the first class in the second class)
from Tkinter import *
class window_1(object):
def __init__(self):
self.app = Tk()
self.app.title("Window One")
def entrybox(self):
self.ent = Entry(self.app) #This is the text i'm trying to get in 2nd class
def button(self):
def ODV(self):
class window_2(object):
def __init__(self):
self.app2 = Tk()
self.app2.title("Window Two")
def labels(self):
self.label_0 = Label(self.app2, text = "Name: ")
def info(self):
self.fetch_name = self.ent.get()#Here is my problem
def gridder(self):
self.label_0.grid(row = 0, column = 0)
self.fetch_name.grid(row = 0, column = 1)
rooter = window_2()
rooter.labels()
rooter.info()
rooter.gridder()
open_data_viewer = lambda: ODV(self)
self.but = Button(self.app, text = "Save", command = open_data_viewer)
def packer(self):
self.ent.pack(anchor = W)
self.but.pack(anchor = W)
def App_Runner(self):
self.app.mainloop()
root = window_1()
root.entrybox()
root.button()
root.packer()
root.App_Runner()
Your first problem is that you're creating more than one instance of Tk. You can't do that, tkinter isn't designed to work that way. If you want multiple windows, create instances of Toplevel. A tkinter program should always have exactly one instance of Tk, exactly one call to mainloop, and there should be little to no code following the call to mainloop.
Second, there is absolutely no value in embedding the definition of a class inside a function. Move it out, it will make your code easier to understand, and easier to write and maintain.
Third, for an instance of one object to access a method on another object, the first object needs to know about the second object or needs to know about a central "controller" object. This isn't a tkinter problem, it's a normal thing to consider when writing OO code.
From a practical standpoint, you need to pass in a reference either to the entry widget, or the object that contains the entry widget, when you create the second object. For example:
class window_2(object):
def __init__(self, other):
...
self.other = other
...
def info(self):
self.fetch_name = self.other.ent.get()
...
rooter = window_2(self) # pass "self" to the new object
This produces a tight coupling between the two objects -- the second object knows about the inner workings of the first object. This is not very good design, though for very, very simple programs it's not so bad. The problem is this: if you change the layout of the first widget, perhaps renaming "self.ent" to "self.some_other_frame.ent", you have to modify the other class too.
A better solution is to define in your first class a function that gets it's own value. Of course, ent serves that purpose, but again, that is a tight coupling. better to have a helper function:
class window_1(object):
...
def get_string(self):
return self.ent.get()
class window_2(object):
def info(self):
self.fetch_name = self.other.get_string()
This still has a loose coupling, but one that is much easier to manage because the coupling isn't tied to the specific internal layout and names of the first window. You can change the widgets all you want, as long as you continue to provide a get_string method that does what the other class expects. Your first class is providing a contract to the second class: a promise that no matter how else the window may change over time, it promises to provide this interface.