Python---Basic Knowledge Review (9) Graphical User Interface

Mainly using wxPython (the most mature cross-platform python GUI toolkit)

Foreplay: Veteran python GUI program (Tkinter)

import tkinter.messagebox as messagebox

class Application(Frame):
    def __init__(self,master=None):
        Frame.__init__(self,master,bg = " red " ) #Set the parent class of the frame class (based on master<main form> ), the frame can be regarded as the parent container of the control
        self.pack() #Display frame control
        self.createWidgets()

    def createWidgets(self): #Used to create widgets (children of frame)
        self.nameInput = Entry(self)
        self.nameInput.pack()
        self.alertButton = Button(self,text="Hello",command=self.hello)
        self.alertButton.pack()

    def hello(self):
        name = self.nameInput.get()
        messagebox.showinfo("Message","Hello, %s"%name)


root = Tk()
root.title( " title " )
root.wm_minsize(200,200)

app = Application(root)

app.mainloop ()

def callback():
    var.set("hhhhhhh")

root = Tk()

var = StringVar()
var.set("66666")


frame1 = Frame(root)
frame2 = Frame(root)


lb = Label(frame1,textvariable=var,padx=20)
lb.pack(side=LEFT)

# img = Image(file="1.gif",imgtype="photo")
img = PhotoImage(file="1.gif")
lb2 = Label(frame1,image=img)
lb2.pack(side=RIGHT)

btnCm = Button(frame2,text= " Next " ,command= callback)
btnCm.pack()

frame1.pack()
frame2.pack()

root.mainloop ()

The use of label tags (using pictures)

from tkinter import *

root =Tk()

v = IntVar() #selected is 1, unselected is 0

c = Checkbutton(root,text="Test",variable=v)
c.pack()

l = Label(root,textvariable=v)
l.pack()

root.mainloop ()

Checkbutton use (1)

from tkinter import *

root =Tk()

GIRLS = ["asd",'dsa','fef','fwaf']

v = []

def change():
    for i in v:
        print(i.get())

for girl in GIRLS:
    v.append(IntVar())
    b = Checkbutton(root,text=girl,variable=v[- 1 ],command= change) #Use an inherent variable to record the status
    b.pack(anchor = W) #The control is on the left relative to the main window


root.mainloop ()

Use of Checkbutton (2)

#For radio boxes, multiple buttons correspond to only one variable, checkboxes, and multiple buttons correspond to multiple values
 ​​from tkinter import *

def change():
    print(v.get())

root = Tk()

v = IntVar ()

Radiobutton(root,text="one",variable=v,value=1,command=change).pack(anchor=W)
Radiobutton(root,text="two",variable=v,value=2,command=change).pack(anchor=W)
Radiobutton(root,text="three",variable=v,value=3,command=change).pack(anchor=W)

root.mainloop ()

The use of Radiobutton (1)

from tkinter import *

def change():
    print(v.get())


root = Tk()
v = IntVar ()

Langes = [
    ("python",1),
    ("javascript",2),
    ("Lua",3),
    ("Ruby",4)
]

for key,val in Langes:
    Radiobutton(root,text=key,variable=v,value=val,command=change).pack(anchor=W)

root.mainloop ()

The use of Radiobutton (2)

#For radio buttons, multiple buttons correspond to only one variable, and for checkboxes, multiple buttons correspond to multiple values ​​(obtained using a list)

Notice:
root = Tk()
v = IntVar ()
All the variables we declare here should be written after the main window is generated.

---

Otherwise, when we write the variable before the main window is generated
v = IntVar ()
root = Tk()
will report an error
AttributeError: 'NoneType' object has no attribute '_root'

1. First enter the IntVar class
 class IntVar(Variable):
    def __init__(self, master=None, value=None, name=None):
        Variable.__init__(self, master, value, name)
2. Enter the parent class
 class Variable:
    def __init__(self, master=None, value=None, name=None):
        ...
        if not master: #Look here (master is the main window, it is a parameter, but we did not pass it in when we used it, so it is empty, enter the following code)
            master = _default_root # what is _default_root
        self._root = master._root()
        self._tk = master.tk
        ...
3 ._default_root lookup
_support_default_root = 1 #Also     useful, see later
_default_root = None # is a global variable representing the main window
But he is also empty, so the above attribute error occurs, None has no _root() method
------------------------------------------------------------------

Start looking at Tk()
root = Tk()
 1 . View the source code
 class Tk(Misc, Wm):
    def __init__(self, screenName=None, baseName=None, className='Tk',
                 useTk=1, sync=0, use=None):
        ...
        if useTk: #Here 1 is passed in by default, and the following logic is entered
            self._loadtk()
       ...
2. View the self._loadtk() method

    def _loadtk(self):
        self._tkloaded = 1
        global _default_root
        # Version sanity checks
        ......
        # Create and register the tkerror and exit commands
        # We need to inline parts of _register here, _ register
        # would register differently-named commands.
        ......
        if _support_default_root and not _default_root: #Check the above global variables and find that you can enter the following logic code
            _default_root = self #So _default_root is the main window
        ......
------------------------------------------------------------------

Conclusion: From the above findings, we can know that:
The use of variables such as IntVar requires _default_root (when we do not pass in master), and when the main window generates root =Tk(), the internal code implements _default_root. Therefore, the order of the two needs to be guaranteed.

Reason: source code analysis

 

 

 

There are other toolkits PyQT and PyGTK are also widely used.