i am quite new to inheritance and overriding methods and i am not quite sure how to override the __init__ method of a class, more specifically, adding another parameter to it.
Basically i want to override the __init__ method of the tkinter class simpledialog.Dialog.
From the documentation the init method of simpledialog.Dialog has the Parameters __init__(self,parent,title=None) and i want it to be __init__(self,parent,labeltitle,title=None)
Ok guys, so for context i also changed some of the other methods of the class, i will give you the code so that people know why i want labeltitle in the init method. I found a solution on how to solve my problem, if anyone has an idea or sees a problem with this let me know.
import tkinter
from tkinter import simpledialog
class MyDialog(simpledialog.Dialog):
def __init__(self,parent,labeltitle,title):
self.labeltitle=labeltitle
super().__init__(parent,title)
def body(self, master):
self.geometry("400x300")
tkinter.Label(master, text=self.labeltitle).grid(row=0)
self.e1 = tkinter.Entry(master)
self.e1.grid(row=0, column=1,pady=30)
return self.e1 # initial focus
def apply(self):
first = self.e1.get()
self.result = first
so now when i create an Object of MyDialog like this:
asd = MyDialog(root,"title_of_the_label","title_of_the_Dialogwindow")
i get the Dialogwindow with these titles. Now i can create multiple objects with different windowtitles and labeltitles, since the simpledialog.Dialog class only allowed to change the title of the Dialogwindow, not the labeltitle.
Related
I don't very understand the classes logic in python but cannot answer on web.
I have create a class to generate person info:
class person:
def fristnameGen(gender):
...
def emailGen(firstname,surname):
...
i create a bot to call it like this:
from person import *
class bots:
def __init__(self):
self.person = person()
def createDB(self):
print(self.person.name)
#do something...
finally i call it by a button with thread
from bots import *
import threading
class Panel:
def __init__(self):
self.top = tk.Tk()
self.bot = bots()
self.buildUI()
def foo(self):
self.bot.createDB(self.stringPhone.get())
def threadTheAction(func, *args):
t = threading.Thread(target=func, args=args)
t.setDaemon(True)
t.start()
def buildUI(self):
Button = tk.Button(self.top, text ="Start", command = lambda :self.threadTheAction(self.foo))
I get this error:
TypeError: 'Panel' object is not callable
However, i call it directly, its work
Button = tk.Button(self.top, text ="Start", command = lambda :self.foo())
How to fix the error?
...
2. Moreover, i tried create p1 = person() and p2= person() and print it. Found p1 and p2 is a same person, i prefer each new a class have a new one. How to generate "new person" using classes?
Thank you
You seem to have a lot of confusion about Object Oriented Programming in Python. Some of your methods have self parameters and some do not, seemingly at random. That's the source of your current error.
The threadTheAction method in your Panel class is getting the Panel instance passed in as its first argument, but that's named func in the method (since you omitted self). The real function you're passing as an argument gets caught in the variable argument *args. When the thread tries unsuccessfully to call it, you get an exception. Adding self before func would fix the immediate problem:
def threadTheAction(self, func, *args):
I suspect if your code got further along, you'd run into other errors with other methods without self in their parameter lists. For instance, none of the methods you've shown in person are likely to work correctly.
As for your second question, you haven't shown enough of person to know what's happening, but you're probably doing instance variables wrong somehow. With no self parameter in the methods, that's almost inevitable (since you assign to self.whatever to set a whatever attribute on the current instance). If you need help squaring that away, I suggest you ask a separate question (Stack Overflow is best when each question is self-contained) and provide the full code for your person class.
I have a couple of child classes that I want to use but they both inherit a method from their parent that doesn't quite behave the way I need it to.
class ParentClass():
def __init__(self, value):
self.value = value
def annoying_funct(self):
print("I don't do quite what's needed and print {0}".format(self.value + 1))
def other_parent(self):
print("I do other useful things my children inherit")
class Child1(ParentClass):
def __init__(self, value, new_value1):
super(Child1, self).__init__(value)
self.new_value1 = new_value1
def other_child1(self):
print("I do useful child things")
class Child2(ParentClass):
def __init__(self, value, new_value2):
super(Child2, self).__init__(value)
self.new_value2 = new_value2
def other_child2(self):
print("I do other useful child things")
I want to overwrite annoying_funct() as something like this:
def annoying_funct():
print("I behave the way I am needed to and print {0}".format(self.value))
ParentClass, Child1 and Child2 are from a very complex library (scikit-learn), so I want to keep all of my wrappers as thin as possible. What would be the cleanest/most pythonic way of getting the functionality of my two child classes while altering the parent class as needed?
My thoughts so far:
Create a new class that inherits from the parent which overwrites the function I don't like and then make wrapper classes for the children that inherit from the new class and the child classes.
class NewParentClass(ParentClass):
def annoying_funct(self):
print("I behave the way I am needed to and print {0}".format(self.value))
class NewChild1(NewParentClass, Child1):
pass
class NewChild2(NewParentClass, Child2):
pass
My areas of confusion:
Is this the correct approach? It seems a little weird and klugy. Is there a cleaner way of doing this?
Is the syntax used for the two child classes correct? It runs for me, but it seems a little weird having them do nothing but inherit and pass.
Is having my new parent inherit from the previous parent the correct way of doing this? The code runs for the children without the inheritance between parentClass and newParentClass (eg. def newParentClass():), but if someone tried to make an instance of newParentClass() the function wouldn't work because it uses attributes not present in that class (value). Is that ok if I assume the class will never be used?
There are a couple of ways to do what you ask.
Create a new class inheriting from the parent class, then use it as new parent class.
The only drawback for this solution is that the when you provide the new parent or child class to functions requiring the original Parent class might not work since they might use annoying_funct and rely on an annoying behavior.
class NewParentClass:
def annoying_funct(self):
print("I behave the way I am needed to and print {0}".format(self.value))
class NewChild1(NewParentClass):
pass
class NewChild2(NewParentClass):
pass
Manipulate the existing Parent class
This is the solution I would like to use since it destroys the annoying_funct completely by replacing it with a well behaving one, buy again, other methods and functions requiring the former annoying_funct might fail. The good side is, you don't need to create another parent class and children, so your code will be much more elegant.
class ParentClass():
...
def annoying_funct(self):
print("I don't do quite what's needed and print {0}".format(self.value + 1))
...
def well_behaving_func(s):
print("Good")
# Dynamically change the class method
ParentClass.annoying_func = well_behaving_func
class Child1(Parent):
pass
class Child2(Parent):
pass
c = Child1()
c.annoying_funct() # prints 'Good'
Add a well behaving new method to parent class before inheriting from it.
If you want to maintain the current behavior and don't want your existing code or packages dependent on the parent class break, you certainly should not overwrite the annoying_funct in the parent class. So you should define a well behaving function and use it in child classes.
class ParentClass():
...
def annoying_funct(self):
print("I don't do quite what's needed and print {0}".format(self.value + 1))
...
def well_behaving_func(s):
print("Good")
# Dynamically change the class method
ParentClass.well_behaving_func = well_behaving_func
class Child1(Parent):
pass
class Child2(Parent):
pass
c = Child1()
# use 'well_behaving_func', not the annoying one
c.well_behaving_func() # prints 'Good'
What I ended up doing was using the concept of a mixin to add my new functionality to the child classes. The resulting code was as follows:
class AnnoyMixin:
def well_behaving_func(self):
print("I behave the way I am needed to and print {0}".format(self.value))
class NewChild1(AnnoyMixin, Child1):
def annoying_funct(self):
return well_behaving_func(self)
class NewChild2(AnnoyMixin, Child2):
def annoying_funct(self):
return well_behaving_func(self)
Functionally, this mostly behaves the same as the code I had proposed in my question, but the modifications help with readability. First, by naming the new parent as a "Mixin" it makes it clear that this class is not designed to stand on its own, but rather is intended to add functionality to another class. Because of this, AnnoyMixin doesn't need to inherit from ParentClass, simplifying inheritance for the NewChild classes.
Second, rather than overwriting annoying_funct in AnnoyMixin, we create the new function well_behaving_func. It is then the NewChild classes job to overwrite annoying_funct by calling well_behaving_func. Functionally, this works more or less the same as if the AnnoyMixin had over written annoying_funct, but this way, it is clearer to those reading the code that annoying_funct is being overwritten in the NewChild classes.
I'm having some doubts with the design of mutiple inheritance in some Python classes.
The thing is that I wanted to extend the ttk button. This was my initial proposal (I'm omitting all the source code in methods for shortening, except init methods):
import tkinter as tk
import tkinter.ttk as ttk
class ImgButton(ttk.Button):
"""
This has all the behaviour for a button which has an image
"""
def __init__(self, master=None, **kw):
super().__init__(master, **kw)
self._img = kw.get('image')
def change_color(self, __=None):
"""
Changes the color of this widget randomly
:param __: the event, which is no needed
"""
pass
def get_style_name(self):
"""
Returns the specific style name applied for this widget
:return: the style name as a string
"""
pass
def set_background_color(self, color):
"""
Sets this widget's background color to that received as parameter
:param color: the color to be set
"""
pass
def get_background_color(self):
"""
Returns a string representing the background color of the widget
:return: the color of the widget
"""
pass
def change_highlight_style(self, __=None):
"""
Applies the highlight style for a color
:param __: the event, which is no needed
"""
pass
But I realized later that I wanted also a subclass of this ImgButton as follows:
import tkinter as tk
import tkinter.ttk as ttk
class MyButton(ImgButton):
"""
ImgButton with specifical purpose
"""
IMG_NAME = 'filename{}.jpg'
IMAGES_DIR = os.path.sep + os.path.sep.join(['home', 'user', 'myProjects', 'myProject', 'resources', 'images'])
UNKNOWN_IMG = os.path.sep.join([IMAGES_DIR, IMG_NAME.format(0)])
IMAGES = (lambda IMAGES_DIR=IMAGES_DIR, IMG_NAME=IMG_NAME: [os.path.sep.join([IMAGES_DIR, IMG_NAME.format(face)]) for face in [1,2,3,4,5] ])()
def change_image(self, __=None):
"""
Changes randomly the image in this MyButton
:param __: the event, which is no needed
"""
pass
def __init__(self, master=None, value=None, **kw):
# Default image when hidden or without value
current_img = PhotoImage(file=MyButton.UNKNOWN_IMG)
super().__init__(master, image=current_img, **kw)
if not value:
pass
elif not isinstance(value, (int, Die)):
pass
elif isinstance(value, MyValue):
self.myValue = value
elif isinstance(value, int):
self.myValue = MyValue(value)
else:
raise ValueError()
self.set_background_color('green')
self.bind('<Button-1>', self.change_image, add=True)
def select(self):
"""
Highlights this button as selected and changes its internal state
"""
pass
def toggleImage(self):
"""
Changes the image in this specific button for the next allowed for MyButton
"""
pass
The inheritance feels natural right to his point. The problem came when I noticed as well that most methods in ImgButton would be reusable for any Widget I may create in the future.
So I'm thinking about making a:
class MyWidget(ttk.Widget):
for putting in it all methods which help with color for widgets and then I need ImgButton to inherit both from MyWidget and ttk.Button:
class ImgButton(ttk.Button, MyWidget): ???
or
class ImgButton(MyWidget, ttk.Button): ???
Edited: Also I want my objects to be loggable, so I did this class:
class Loggable(object):
def __init__(self) -> None:
super().__init__()
self.__logger = None
self.__logger = self.get_logger()
self.debug = self.get_logger().debug
self.error = self.get_logger().error
self.critical = self.get_logger().critical
self.info = self.get_logger().info
self.warn = self.get_logger().warning
def get_logger(self):
if not self.__logger:
self.__logger = logging.getLogger(self.get_class())
return self.__logger
def get_class(self):
return self.__class__.__name__
So now:
class ImgButton(Loggable, ttk.Button, MyWidget): ???
or
class ImgButton(Loggable, MyWidget, ttk.Button): ???
or
class ImgButton(MyWidget, Loggable, ttk.Button): ???
# ... this could go on ...
I come from Java and I don't know best practices for multiple inheritance. I don't know how I should sort the parents in the best order or any other thing useful for designing this multiple inheritance.
I have searched about the topic and found a lot of resources explaining the MRO but nothing about how to correctly design a multiple inheritance. I don't know if even my design is wrongly made, but I thought it was feeling pretty natural.
I would be grateful for some advice, and for some links or resources on this topic as well.
Thank you very much.
I've been reading about multiple inheritance these days and I've learnt quite a lot of things. I have linked my sources, resources and references at the end.
My main and most detailed source has been the book "Fluent python", which I found available for free reading online.
This describes the method resolution order and design sceneries with multiple inheritance and the steps for doing it ok:
Identify and separate code for interfaces. The classes that define methods but not necessarily with implementations (these ones should be overriden). These are usually ABCs (Abstract Base Class). They define a type for the child class creating an "IS-A" relationship
Identify and separate code for mixins. A mixin is a class that should bring a bundle of related new method implementations to use in the child but does not define a proper type. An ABC could be a mixin by this definition, but not the reverse. The mixin doesn't define nor an interface, neither a type
When coming to use the ABCs or classes and the mixins inheriting, you should inherit from only one concrete superclass, and several ABCs or mixins:
Example:
class MyClass(MySuperClass, MyABC, MyMixin1, MyMixin2):
In my case:
class ImgButton(ttk.Button, MyWidget):
If some combination of classes is particularly useful or frequent, you should join them under a class definition with a descriptive name:
Example:
class Widget(BaseWidget, Pack, Grid, Place):
pass
I think Loggable would be a Mixin, because it gathers convenient implementations for a functionality, but does not define a real type. So:
class MyWidget(ttk.Widget, Loggable): # May be renamed to LoggableMixin
Favor object composition over inheritance: If you can think of any way of using a class by holding it in an attribute instead of extending it or inheriting from it, you should avoid inheritance.
"Fluent python" - (Chapter 12) in Google books
Super is super
Super is harmful
Other problems with super
Weird super behaviour
In principle, use of multiple inheritance increases complexity, so unless I am certain of its need, I would avoid it. From your post you already look aware of the use of super() and the MRO.
A common recommendation is to use composition instead of multiple inheritance, when possible.
Another one is to subclass from only one instantiable parent class, using abstract classes as the other parents. That is, they add methods to this subclass, but never get instantiated themselves. Just like the use of interfaces in Java. Those abstract classes are also called mixins, but their use (or abuse) is also debatable. See Mixins considered harmful.
As for your tkinter code, besides logger code indentation, I don't see a problem. Maybe widgets can have a logger instead of inheriting from it. I think with tkinter the danger is the unwanted override by mistake of one of the hundreds of available methods.
I have a small problem with my code.
There are two classes. First one creates a window with a Options button. Upon clicking the button, the second class is called and creates another window with an Ok button. Let's say there is also a checkbox, which changes the background color to black or something like that. After clicking the button, whatever changes were made in the options are stored into a file and the second window is closed.
All of this works fine. My problem is that now I need to call method update_init from the first class that will apply those changes to the MainWindow. The code below shows my first solution to this problem, but from what I understand, by using second mainloop I create second thread, which should be avoided.
class MainWindow:
def __init__(self, master):
self.master = master
self.options_btn = tk.Button(self.master, text="Options", command=self.open_options)
self.options_btn.pack()
self.options_window = None
def open_options(self):
options_master = tk.Toplevel()
self.options_window = OptionsWindow(options_master)
options_master.mainloop()
lst = meta_load() # loads changes from a file
self.update_init(lst)
def update_init(self, lst):
#code
class OptionsWindow:
def __init__(self, master):
self.master = master
self.ok_btn = tk.Button(self.master, text="OK", command=self.update_meta)
self.ok_btn.pack()
def update_meta(self):
meta_save(12) # saves changes into a file
self.master.destroy()
main_master = tk.Tk()
main_master.minsize(width=1280, height=720)
b = MainWindow(main_master)
main_master.mainloop()
My second solution was to just put both classes into one, but the code is quite messy if I do so.
Can I somehow call the method update_init (which is in the MainWindow class) from the OptionsWindow class without initializing new MainWindow class window? Or is there any other way to deal with this? I would appreciate any help.
I am sorry if this is too specific, I've tried to make it as general as possible, but it's a very specific problem and I couldn't find much information about it anywhere on the internet.
In general you can call a class method from anywhere you want and pass anything to it without initialisation of that class's instance, thanks to objective nature of python, but beware of self dependencies! Although, I don't think that's a good practice.
class A:
def __init__(self):
self.foo = 'foo'
def return_foo(self):
return self.foo
class B:
def __init__(self):
self.bar = 'bar'
print('Ha-ha Im inited!')
def return_bar(self):
try:
return self.bar
except AttributeError:
return 'bar'
def test():
a = A()
# b = B()
return_bar = getattr(B, 'return_bar', None)
if callable(return_bar):
print('%s%s' % (a.return_foo(), return_bar(None)))
test()
Links:
getattr
callable
Hi I've been struggling to get this to work, each time i change something I receive another error. I've been trying to create an entry box with a function and then get the variable from the entry box into a label, created by a button press. When I tried to do this often this error came up.
TypeError: get() missing 1 required positional argument: 'self'
I then put self in in the method brackets.
command = lambda: x.myFunc(self.my_variable.get(self))
Then another error, which I'm not sure how to sort out.
AttributeError: 'My_Class' object has no attribute '_tk'
Here's the full code, I'm new to classes and self, so any corrections are welcome.
from tkinter import *
import time
class My_Class:
def start(self):
self.root=Tk()
self.my_variable=StringVar
self.entry_box=Entry(self.root, textvariable=self.my_variable)
self.entry_box.pack()
self.button=Button(self.root,text="Pass variable now",
command=lambda:x.myFunc(self.my_variable.get(self)))
self.button.pack()
def myFunc(self,my_variable):
self.lab=Label(self.root,text=self.my_variable)
self.lab.pack()
x=My_Class()
x.start()
This is the correct way to create a StringVar object:
text = StringVar() # note additional ()
Can you explain me what x is in the following statement:
lambda: x.myFunc(self.my_variable.get(self))
x is not visible inside the class, because it's declared outside the class.
myFunc is not indented correctly: you should indent it like the __init__ method.
I really recommend you to watch some tutorials on OOP before proceeding. You are basically trying to guess how OOP works.
If you make myFunc A method if the class (which you might be trying to do; it's hard to know because your indentation is wrong), you don't have to pass anything to myFunc. That function has access to everything in the class, so it can get what it needs, when it needs it. That lets you eliminate the use of lambda, which helps reduce complexity.
Also, you normally don't need a StringVar at all, it's just one more thing to keep track of. However, if you really need the label and entry to show exactly the same data, have them share the same textvariable and the text is updated automatically without you having to call a function, or get the value from the widget, or set the value n the label.
Here's an example without using StringVar:
class My_Class:
def start(self):
...
self.entry_box = Entry(self.root)
self.button = Button(..., command = self.myFunc)
...
def myFunc(self):
s = self.entry_box.get()
self.lab = Label(..., text = s)
...