Using Tkinter (python3.6) Implement a Simple Calculator

Preface

The practical course on the computer began,嗯，After the teacher came, he read through the PPT and then said: Start working......

Then, I embarked on the journey of Python's GUI, having never been exposed to Python's visual interface before (though it was not very wise to do so)

But now it feels quite convenient to write small tools, and the first library I found was Tkinter, so I started writing directly

Later, it was found that QT is quite good, so the next experiment will use QT. Then, regarding Tkinter (Python3.6)

Calculator source code ennn.....Some names are not standardized......

Firstly, the implementation of stack in Python is simulated through the use of a list

pop() out of the stack, append() into the stack

First, let's take a look at the commonly used core small component classes provided by Tkinter:

Small component class	Description
Button	Button
Canvas	Structured graphics, used for drawing graphics, creating graphic editors, and implementing custom small component classes
Checkbutton	Click the checkbox to toggle between values
Entry	Text field or text box
Frame	Container (can contain other small components)
Label	Displays text or images
Menu	Menu bar that displays dropdown menus and popup menus
Menubutton	Menu button of dropdown menu
Message	Similar to label display text, but can automatically place text within the given width and height
Radiobutton	Radio button
Text	Formatted text display, supports embedded images and text, and allows displaying and editing text with different styles and properties

Start a window

When making a visual thing, the first thing that comes to mind is definitely a window

A window has many components, such as title, ico, size, bd, and menus.

import tkinter
import os
from tkinter import *
class Calculator(object):
 """Calculator"""
 def __init__(self):
 self.tk=tkinter.Tk() #Instance
 self.tk.title('Calculator')
 self.tk.minsize(370,460)
 self.tk.maxsize(400,400)
 #You can also use self.tk.resizable(0, 0) to disable resizing
 self.tk.iconbitmap(os.getcwd())+'/favicon.ico')
 def start(self):
 self.tk.mainloop() 
if __name__ == '__main__':
 NewCalculator=Calculator()
 NewCalculator.start()

Here, a basic window is generated, and the role of mainloop() within it

If we delete it, the window will flash and disappear, and it is designed to prevent this situation

Panel display

After making a calculator, it is definitely necessary to show the calculation result first, which requires generating a display panel here

Of course, we will also naturally associate with the font settings of displayed content and other specific needs, with examples shown in the following code

....
import tkinter.font as tkfont
....
 #Font settings
 self.EntryFont=tkfont.Font(self.tk, size=...13)
 self.ButtonFont=tkfont.Font(self.tk, size=...12)
 #Panel display
 self.count=tkinter.StringVar()
 self.count.set('0')
 self.label=tkinter.Label(self.tk,bg='#EEE9E9',bd='3',fg='black',anchor='center',font=self.EntryFont,textvariable=self.count)
 self.label.place(y=10,width=380,height=40)
....

Among them, there are some parameters in the panel Lable of tkinter, and the ones used here basically meet the common needs

Among them, bg is the background color, fg is the foreground color, changing the color of the content, anchor is the position of the content in the panel, as shown in the figure below

direction	example	table
nw	n	ne
w	center	e
sw	s	se

Regarding the positioning of the panel and the Button behind, many methods can be used, place can accurately locate, and also pack(), grid() can be used

It is better for the calculator to use place, which can accurately locate each control

The font can also be directly added as a parameter in Lable(), for example, font=("Arial,6")

textvariable is equivalent to the role of 'listening', binding tkinter's string, you can change the content of the panel conveniently with the set() method

button, input box settings

button, the parameters of the input box and the panel inside are similar

self.NumButton=tkinter.Button(master=self.tk,relief=GROOVE,bg='#EE6A50',text=self.ButtonList[0],
 font=self.ButtonFont,command=self.clear)
self.NumButton.place(x=30,y=80,width=70,height=55)
self.shiEntry=Entry(self.baoxianTk,validate='key',validatecommand=(self.checkNum,'%P'),font=self.EntryFont)
self.shiEntry.place(x=190,y=80)

The same is through the setting of parameters such as bg to establish the basic style, but here it will bind events through command, similar to the .click in JQ

The place here is also used to be able to accurately locate, and the relief represents the style of the Button

relief=FLAT or GROOVE or RAISED or RIDGE or SOLID or SUNKEN

Among which, delete the input content of the input box

text.delete(10) # Delete index value10the value
text.delete(10, 20) # Delete index values from10to2Values before 0
text.insert(0, END) # Delete all values

Input restriction

When designing features, we may need users to input numbers, etc., here we can limit this

The Button parameter specifies when to execute the function bound by validatecommand, using %P can obtain the input content in real time

When the validate option is specified as key, any input operation will be intercepted, at this time returning True will allow the white energy to be input into the Entry

self.checkNum=self.baoxianTk.register(self.validateNum)
self.gerenEntry=Entry(self.baoxianTk,validate='key',validatecommand=(self.checkNum,'%P'),font=self.EntryFont)
self.gerenEntry.place(x=190,y=190)
# Validate if the input is a number 
def validateNum(self,content):
 if content.isdigit() and int(content)>=0 or content=="":
 return True
 else:
 return False

The validateNum() function can be changed according to your needs

The values that can be set for the validate option to enable validation are:

Name	event
focus	Validate when the Entry component gains or loses focus
focusin	Validate when the Entry component gains focus
focusout	Validate when the Entry component loses focus
key	Validate when the input box is edited
all	Validate when any of the following situations occur

Symbol design expansion

I have added % in this small calculator/, symbols such as sqrt

My approach for their implementation is to check the content of the button passed before adding it to the panel

If it is one of these three symbols, corresponding treatment should be given

Among which, if it is a multi-digit number or a number with a sign

Cannot be transformed directly, you need to judge the number of digits of the number you want to transpose, and my specific method is as follows

 def checkList(self):
 result=0
 locate=-1
 listSum=0
 for length in range(0,len(self.inputlist)):
 if re.findall(r'[-+*/]',str(self.inputlist[length])):
 result=1
 if length>locate:
  locate=length
 else:
 pass
 if result==1:
 for i in range(locate+1,len(self.inputlist)):
 listSum+=int(self.inputlist[i])*(10**(len(self.inputlist)-i-1))
 else:
 for j in range(0,len(self.inputlist)):
 listSum+=int(self.inputlist[j])*(10**(len(self.inputlist)-j-1))
 return listSum,locate
 # Add button
 def addButton(self,button):
 if button==self.ButtonList[18]:
 listSum,locate=self.checkList()
 if locate==-1:
 self.inputlist=[str(round(eval('1/'+str(listSum)),5))]
 else:
 for k in range(locate+1,len(self.inputlist)):
  del self.inputlist[k]
 self.inputlist.append(str(round(eval('1/'+str(listSum)),5))
 elif button==self.ButtonList[19]:
 pass
 elif button==self.ButtonList[20]:
 pass
 else:
 self.inputlist.append(button)
 self.count.set(self.inputlist)

About lambda

Baidu Encyclopedia: Lambda expression is a special form of function definition in Python, which can be used to define an anonymous function

Unlike other languages, the function body of Python's Lambda expression can only have a single statement, which is the return value expression statement

After searching for more articles, I understand more, Lambda function can be said to play a 'callback' role for the button

If we do not use Lambda for intermediate function delay callback, the function bound to command will be called at the same time as creating the button

The difference between the following two lines of code is that the second line directly executes the knobDown function when creating

self.NumButton=tkinter.Button(master=self.tk, relief=GROOVE, bg='#BFEFFF', text=self.ButtonList[20], font=self.ButtonFont, command=lambda:self.knobDown(self.ButtonList[20))
self.NumButton=tkinter.Button(master=self.tk, relief=GROOVE, bg='#BFEFFF', text=self.ButtonList[20], font=self.ButtonFont, command=self.knobDown(self.ButtonList[20))

For a more detailed explanation, you can refer to the last two articles at the end, the predecessors write well

About the radio button

I wanted to implement the example given in the PPT-The extension of mortgage calculation, but I gave up because of the BUG in this radio button

The following example is copied from the internet, but I forgot the specific URL

It is through the variable binding an IntVar() that the value of the Radiobutton can be obtained through the .get() method

#!/usr/bin/env python
import tkinter
from tkinter import *
import tkinter.font as tkfont
root=tkinter.Tk()
val=tkinter.IntVar()
val.set(0)
def func1
 if val.get() == 0:
 label.configure(text='radio 0')
 else:
 label.configure(text='radio 1
label = tkinter.Label(root, text='radio 0')
label.pack()
r0 = tkinter.Radiobutton(text = 'radio0', variable = val, value = 0)
r0.pack()
r1 = tkinter.Radiobutton(text = 'radio1variable = val, value = 1)
r1.pack()
b = tkinter.Button(root, text='button', command=func1)
b.pack()
root.mainloop()

Packaging

C:\Users\bayi\Desktop\shiyan\progrem
(venv) λ pip install pyinstaller
C:\Users\bayi\Desktop\shiyan\progrem
(venv) λ pyinstaller -F -w -i favicon.ico run.py

At first, because the code set the ico icon to the following code in the first line

There is a problem with the path recognition of the packaging path under Windows, so move the icon to a place with a short path

Modify it to an absolute path and it's OK (the second line of the code below, exe and ico should be placed in the same directory)

self.baoxianTk.icobitmap('favicon.ico')
self.baoxianTk.iconbitmap(os.getcwd())+'/favicon.ico')

Preview of the effect

Although it is learned on the spot and based on others' old knowledge, it is still very rewarding after success (and I seem to be very picky about graphic design...)

It takes a long time to adjust colors and styles, including the front-end of the previous crawler

Summary

That's all for this article. I hope the content of this article has certain reference value for everyone's learning or work. If you have any questions, you can leave a message for communication. Thank you for your support of the Yell Tutorial.

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