DEV Community: Anjali Kumawat

GUI in Python Using Tkinter

Anjali Kumawat — Fri, 10 Dec 2021 08:11:11 +0000

GUI in Python

Python libraries to create Graphical Interfaces :

Tkinter
Python QT
wxPython
Kivy

Tkinter is an inbuilt Python module used to create simple GUI apps.

Tk provides following widgets :

button
canvas
checkbutton
Combobox
entry
frame
label
labelframe
listbox
menu
menubutton
message
notebook
tk_optionmenu
panedwindow
progressbar
radiobutton
scale
scrollbar
separator
sizegrip
spinbox
text
treeview

It provided the following top-level windows :

tk_chooseColor
tk_chooseDirectory
tk_dialog
tk_getOpenFile
tk_getSaveFile
tk_messageBox
tk_popup
toplevel

Tk also provides three geometry managers :

place - It positions widgets at absolute locations
grid - It arranges widgets in a grid
pack - It packs widgets into a cavity

Basics of tkinter

import tkinter module
create the main window (container)
Add any number of widgets to the main window
Enter the main event loop

Eg.

import tkinter
window = Tkinter.Tk()          # creates main window
window.title("GUI")
label = tkinter.Label(window , text="Hello World !!").pack()
window.mainloop()

mainloop() is used when our application is ready to run. mainloop() is an infinite loop used to run the application, wait for an event to occur and process the event till the window is not closed.

Widgets

Button

It is used to add a button in our application.

window = Button(master, option=value)

master represents the parent window.

activebackground : sets the background color when button is under the cursor.

activeforeground : sets the foreground color when button is under the cursor.

bg : sets normal background color

fg : sets the foreground color

command : to call a function

font : sets the font of button label

image : sets the image on the button

width : sets the width of the button

height : sets the height of the button

justify : LEFT , RIGHT , CENTER

import tkinter as tk
window = tk.Tk()
window.title("Python")
button = tk.Button(window , text = 'GUI',width = 25,command = window.destroy)
button.pack()
window.mainloop()

Output is :

Label

It is used to display text or image.

window = Label(master,option=value)

bg : sets the normal background color
command : to call a function
font : sets the font of Label text
image : sets the image on the Label
width : sets the width of the Label

height : sets the height of the Label

from tkinter import *
root = Tk()
l1 = Label(root,text="GUI Python",bg="pink",width = 25)
l1.pack()
root.mainloop()

Output is :

Entry

(Text Field)

It is used to input single line of text.

window = Entry(master,option=value)

bg : sets the background color

fg : sets the foreground color

font : sets the font for widget

justify : LEFT , RIGHT , CENTER

command : to call a function

width : sets the width of widget

height : sets the height of widget

show : Normally, the characters that the user types appear in the entry. To make a .password. entry that echoes each character as (show = "*")

Methods of Entry

delete(start,end) : delete a character or range of characters

get() : returns the text of widget

insert(index,string) : inserts text at the specified index

select_range(start,end) : selects specified range.

select_present() : returns True if there is a selection,false otherwise

from tkinter import *
master = Tk()
l1=Label(master,text='first Name')
l1.grid(row=0)
l2=Label(master,text='Last Name')
l2.grid(row=1)
e1=Entry(master)
e2=Entry(master)
e1.grid(row=0,column=1)
e2.grid(row=1,column=1)
mainloop()

Output is :

Text

It is used to edit multi line text and formate the way it has to be displayed.

t = Text(master,option = value)

highlightcolor : set the color of focus highlight

insertbackground : set the background of the widget

bg : sets the normal background color

fg : sets the foreground color

bd : sets width of the border around the widget. (Default is 2 pixels)

font : sets the font

image : sets the image

width : sets the width (in pixels)

height : sets the height (in lines)

from tkinter import *
root = Tk()
t = Text(root , height = 4,width=40)
t.pack()
t.insert(END,'ANJALI KUMAWAT \nCOMPUTER SCIENCE UNDERGRAD \nGWOC"21" CONTRIBUTOR')
mainloop()

Output is :

Methods of Text

delete(start,end) - deletes a specific character or a range of text
get(start,end) - returns a specific character or a range of text
insert(index,string) - inserts text at the specified index

CheckButton

It is used to display a number of options to a user as toggle buttons.

window = CheckButton(master , option = value)

bg : sets background color

fg : sets foreground color

command : to call a function

font : sets the font

image : sets the image

cffvalue : A checkbutton's associated control variable will be set to 0 when it is cleared(off).We can supply an alternate value for the off state.

onvalue : A checkbutton's associated control variable will be set to 1 when it is set(on).We can supply an alternate value for the on state.

state : Default is state=NORMAL but we can use state=DISANLED to grey out the control and make is unresponsive.

variable : This is control variable associated with checkbutton that tracks the current state of widget.Normally this variable is an IntVar and 0 means cleared and 1 means set.

Width : sets the width of widget.

Methods of checkbutton

Deselect() - clears the checkbutton
Select() - selects the checkbutton
Toggle() - reverses the state(on/off)

from tkinter import *
root = Tk()
var1 = IntVar()
var2 = IntVar()
c1 = Checkbutton(root,text = "like Mango ? ",variable = var1,onvalue = 1,offvalue = 0,width = 40)
c2 = Checkbutton(root,text = "like Orange ? ",variable = var2,onvalue = 1,offvalue = 0,width = 40)
c1.pack()
c2.pack()
root.mainloop()

Output is :

RadioButton

It is used to offer multiple choice option to the used and user can select one option.

window = RadioButton(master,option=value)

bg : sets the background color

fg : sets foreground color

command : to call a function

font : sets the font

image : sets the image

width : sets the width

variable : variable associated with the Radiobuttons.

value : when a radiobutton is selected by user,its control variable is set to its associated value. If the control variable is an IntVar , give each radiobutton in the group a different integer value option. If the control variable is a StringVar,give each radiobutton a different string value option.

Methods of Radiobutton

select() - selects Radiobutton
deselect() - deselects Radiobutton

from tkinter import *

def select():
    if choice.get()==1:
        order = "Large Pizza"
    elif choice.get()==2:
        order = "Medium Pizza"
    else:
        order = "Small Pizza"
    selection = "You have ordered "+order
    label.config(text=selection)

root = Tk()
root.title("Pizza Corner")
choice = IntVar()
rbLarge = Radiobutton(root, text = "Large Pizza",font=20,variable=choice,value=1,command=select)
rbMedium = Radiobutton(root, text = "Medium Pizza",font=20,variable=choice,value=2,command=select)
rbSmall = Radiobutton(root, text = "Small Pizza",font=20,variable=choice,value=3,command=select)
rbLarge.pack(anchor=W)
rbMedium.pack(anchor=W)
rbSmall.pack(anchor=W)
label = Label(root,text="Choose pizza that you want!!",font=35)
label.pack()
mainloop()

Output is :

When we are not clicking on any RadioButton -

If we are clicking on any RadioButton then -

SpinBox

It is used to select a value from fixed number of values.

window = Spinbox(root,option=value)

bg : sets the background color

fg : sets foreground color

font : sets the font

justify : LEFT,RIGHT,CENTER

width : sets the width for widget

from_ : sets the minimum value

to : sets the maximum value

Methods for Spinbox

get() - returns the value

from tkinter import *

def select():
    string = "Selection is "+str(sp.get())
    l.config(text=string)

root = Tk()
sp = Spinbox(root,from_=0,to=10,command=select,width = 15,font=30)
sp.pack()
l=Label(root,text=" ")
l.pack()
mainloop()

Output is :

Keep Learning......
Keep Coding......👩‍💻❤️🙌

EOL : Python Syntax Error

Anjali Kumawat — Tue, 16 Nov 2021 18:27:11 +0000

EOL

EOL == End Of Line

An EOL error indicatesthat Python interpreter expected a particular character or set of characters to have occurred in specific line of code, but that those characters were not found before the end of the line . This results in Python stopping the program execution and throwing a syntax error .The EOL error signifies that the Interpreter of Python reached the end of the line while scanning the string literal.

syntaxerror : Eol while scanning string literal

Let’s take a look at our error:

syntaxerror: EOL while scanning string literal

If a syntax error is encountered, Python stops executing a program and gives a error . This is because the Python interpreter needs you to rectify the issue before it can read the rest of your code.

This error is commonly caused by:

Strings that span multiple lines using the wrong syntax
Missing quotation marks
Mismatching quotation marks

What is String Literal in Python?

String literal is a set of characters enclosed between quotation marks (“). All the characters are noted as a sequence. In Python, you can declare string literals using three types, single quotation marks (‘ ‘), double quotation marks (” “), and triple quotation marks (“”” “””). Strings are arrays and their characters can be accessed by using square brackets.

String Literal Example

exampleA = 'Single Quotes String'
exampleB = "Single Quotes String"
exampleC = """Single Quotes String"""

print(exampleA[0])  # it will print S

Example : Multiple Lines String

In Python, strings can span multiple lines. Multi-line strings must be triple quoted, or written using three quotation marks.

let's look at multiple line string -

def Coder():
    message = "Welcome, Coders!
When to use iterative development? You should use iterative development only on projects that you want to succeed."
        print(message)

Coder()

Output is -

SyntaxError: EOL while scanning string literal

An error is returned because a string using single or double quotes cannot span multiple lines. To solve this problem, we need to enclose our string with three single or double quotes.

Now look at the correct code -

def Coder():
    message = """Welcome, Coders!
When to use iterative development? You should use iterative development only on projects that you want to succeed."""
        print(message)

Coder()

Output is -

Welcome, Coders!
When to use iterative development? You should use iterative development only on projects that you want to succeed.

Example : Missing Quotation Mark

Strings must be closed after the contents of a string have been declared. Otherwise, Python returns a syntax error.

Let’s take a look at a string that is not closed:

def Coder():
    message = "Welcome, Coders!
        print(message)

Coder()

Let's check the output -

SyntaxError: EOL while scanning string literal

An We have forgotten to close our string. If you look at the line of code where we declare the “message” variable, there is no closing string character.
We can fix this error by closing our string using the same quotation mark that we used to open our string.

def Coder():
    message = "Welcome, Coders!"
        print(message)

Coder()

Output -

Welcome, Coders!

Now code runs successfully.

Example : Mismatching Quotation Marks

The type of quote you use to open a string should be the same as the type of quote you use to close a string.

A syntax error is returned when the types of quotes that you use to open and close a string are different. Let’s take a look at a program that opens a string using a single quote mark (‘) and closes a string using a double quote mark (”) :

def Coder():
    message = 'Welcome, Coders!"
        print(message)

Coder()

Output -

SyntaxError: EOL while scanning string literal

We can fix this problem by making our quotations match. We’re going to change our first quotation mark to use double quotes (“):

def Coder():
    message = "Welcome, Coders!"
        print(message)

Coder()

Output -

Welcome, Coders!

Now our code runs successfully.

Conclusion: EOL While Scanning String Literal

Strings have helpful in thousands of ways in Python. As using them can provide easy access to a sequence of characters and their attributes. The only problem is that you have to take care of their syntax. Any invalid syntax and invalid backslashes in the string can cause EOF errors to appear. To avoid this error, follow all the steps from the post above.

Keep Coding......
Keep learning......💻

Python : OS Module

Anjali Kumawat — Wed, 10 Nov 2021 18:07:33 +0000

The os module is a part of the standard library, or stdlib, within Python 3.

Python os module provides methods that help us to perform file processing operations. Let’s explore these basic functions one by one.

Using os

Before you use the os module, you first need to bring it up by means of the Python import command:

import os

If you try to run os without importing it, you will see an error message:

NameError: name 'os' is not defined

To get a list of functions supported by os module, run the below command:

print(dir(os))

Files

Some of the methoods of the os module to work with files.

rename() method :

It is used to rename a file or directory.

os.rename(old_filename,new_filename)

Example

os.rename(“file.txt”, “user.txt”)

remove() method :

It is used to delete the file.
Path : This is a path-like object which represents a file system path. This path-like object is either a string or bytes object.

os.remove(path_of_file)

Example

os.remove(“d1/user.txt”)

Directories

CWD :

CWD == "Current working directory"

getcwd() method :

returns current directory.
or
To check the path of the current working directory, we will use the getcwd method.

print(os.getcwd())

Note The folder where the Python script is running is known as the Current Directory. This is not the path where the Python script is located.

mkdir() method :

It is used to create a directory in current directory.

os.mkdir("d1")

This method raises FileExistsError if the directory to be created already exists.

chdir() method :

Suppose, we have a folder, for example, info, inside our current directory, we can switch to the info folder, using the chdir function. or It is used to change the current directory.

os.chdir("info")

rmdir() method :

It is used to delete a directory. The directory must be empty before it is deleted.

os.rmdir("dirname")

listdir() method :

Returns a list containing names of files and subdirectories in the specified directory.

print(os.listdir())

Keep Learning!!
Keep Coding....❤️👩‍💻

How to Overcome from TLE Error in competitive programming?

Anjali Kumawat — Sun, 07 Nov 2021 18:30:01 +0000

What is TLE?

TLE == "Time Limit Exceed"

Many programmers always argue that the problems in Competitive Programming always end up with TLE(Time Limit Exceed). The main problem with this error is that it will not allow you to know that your solution would reach to correct solution or not!

The main problem in TLE is, you will not be able to know whether your code is generating the right output or not. and when output is right and that time code gives TLE ,the online judge has to stop your submission from running after a particular time period.

Because they first check your compiler error (if any) then runtime error (if any), then TLE (if any) and at last right or wrong answer your code is generating.

Why TLE comes?

To understand Time Limit Exceeded(TLE), understanding how the online judge works will help. The online judge allocates resources like memory and CPU for evaluating every submission.

There might be various reasons behind it that your TLE is coming. Few points are :

Online Judge :

An online judge ( Problem setter the problem) gives TLE on a problem because there are some restrictions in each input with a specific time limit. If your program exceeds that time limit you will get TLE.

Your program is too slow :

The most common reason that you would get a TLE is because your program is too slow.
Read the bounds in the input carefully before writing your program, and try to figure out which inputs will cause your program to run the slowest.

In Python, you could try speeding up your solutions by adding the following two lines to the start of your file:

import psyco
    psyco.full()

To add fast IO in your code you have to write the following lines in main() in your code in C/C++:

ios_base::sync_with_stdio(false); 
    cin.tie(NULL) ;

Java Do not use Scanner class, use BufferedReader instead.

Server Configuration:

Sometimes, the server takes time to run your code. So, it might depend on their CPU, OS, etc. For this reason, the different platform (different servers like practice, CodeChef , HackerEarth etc..)gives you TLE in different cases.
By estimating the maximum value of N (N is the total number of instructions of your whole code), you can roughly estimate the TLE would occur or not in 1 sec.

MAX value of N                       Time complexity
   10^8                              O(N) Border case
   10^7                     O(N) Might be accepted
   10^6                              O(N) Perfect
   10^5                              O(N * logN)
   10^4                              O(N ^ 2)
   10^2                              O(N ^ 3)
   10^9                              O(logN) or Sqrt(N)

Note a loop value (N) cannot be greater than 10^9 if N is an integer. Because an integer can take up to 10^9.

So after analyzing this Table you can estimate your Time complexity roughly and try to make your code within the upper bound limit.

DEV Community: Anjali Kumawat

GUI in Python Using Tkinter

GUI in Python

Basics of tkinter

Widgets

Button

Label

Entry

Methods of Entry

Text

Methods of Text

CheckButton

Methods of checkbutton

RadioButton

Methods of Radiobutton

SpinBox

Methods for Spinbox

EOL : Python Syntax Error

EOL

syntaxerror : Eol while scanning string literal

What is String Literal in Python?

Example : Multiple Lines String

Example : Missing Quotation Mark

Example : Mismatching Quotation Marks

Conclusion: EOL While Scanning String Literal

Python : OS Module

Using os

Files

rename() method :

remove() method :

Directories

CWD :

getcwd() method :

mkdir() method :

chdir() method :

rmdir() method :

listdir() method :

How to Overcome from TLE Error in competitive programming?

What is TLE?

Why TLE comes?

Online Judge :

Your program is too slow :

Server Configuration:

All the best !!

Keep Coding......❤