100 Days Of Python - Day 27

Posted Sep 8, 2023

By Ndimofor Aretas 10 min read

Day 27

Optional and defualt arguments in functions

Optional arguments

when we define a function with optional arguments, we can set default values for the optional arguments.
when we call the function, we can pass values for the optional arguments.
if we do not pass values for the optional arguments, the default values will be used.

  
# main.py
def greet(name="User", location="Earth"):
    print(f"Hello {name}")
    print(f"What is it like in {location}?")

greet() # Hello User
        # What is it like in Earth?
greet("John", "Mars") # Hello John
                      # What is it like in Mars?

If we pass just one argument, the first argument will be assigned to the first optional argument and the second optional argument will be assigned the default value.

  
# main.py
def greet(name="User", location="Earth"):
    print(f"Hello {name}")
    print(f"What is it like in {location}?")

greet("John") # Hello John
              # What is it like in Earth?

Default arguments

when we define a function with default arguments, we can set default values for the default arguments.
when we call the function, we can pass values for the default arguments.
if we do not pass values for the default arguments we will get an error.

  
# main.py
def greet(name, location="Earth"):
    print(f"Hello {name}")
    print(f"What is it like in {location}?")

greet("John") # Hello John
              # What is it like in Earth?

greet() # TypeError: greet() missing 1 required positional argument: 'name'

Unlimited positional arguments

`*args`

*args is a parameter that allows us to pass an arbitrary number of arguments to a function.
*args is short for arguments.
*args returns a tuple.
For example, if we pass 1, 2, 3, 4, 5 to the function, *args will return (1, 2, 3, 4, 5).

  
# main.py

def add(*args):
    total = 0
    for n in args:
        total += n
    return total

print(add(1, 2, 3, 4, 5)) # 15

`**kwargs`

**kwargs is a parameter that allows us to pass an arbitrary number of keyword arguments to a function.
**kwargs is short for keyword arguments.
**kwargs returns a dictionary (with the keyword as the key and the value as the value)
For example, if we pass add=3 and multiply=2 to the function, **kwargs will return {'add': 3, 'multiply': 2}.

  
# main.py

def calculate(n, **kwargs):
    print(kwargs) # {'add': 3, 'multiply': 2}
    for key, value in kwargs.items():
        print(key) # add
                   # multiply
        print(value) # 3
                     # 2
    n += kwargs["add"]
    n *= kwargs["multiply"]
    print(n) # 15

calculate(2, add=3, multiply=2) # 15

*args and **kwargs are just conventions and we can use any name we want.

  
# main.py

# *args
def add(*numbers):
    total = 0
    for n in numbers:
        total += n
    return total

print(add(1, 2, 3, 4, 5)) # 15

# **kwargs

def calculate(n, **operations):
    print(operations) # {'add': 3, 'multiply': 2}
    for key, value in operations.items():
        print(key) # add
                   # multiply
        print(value) # 3
                     # 2
    n += operations["add"]
    n *= operations["multiply"]
    print(n) # 15

calculate(2, add=3, multiply=2) # 15

*args collects positional arguments as a tuple.

Creating a class with optional arguments

  
# main.py

class Car:
    def __init__(self, **kw):
        self.make = kw.get("make")
        self.model = kw.get("model")

my_car = Car(make="Nissan", model="GT-R")
print(my_car.make) # Nissan
print(my_car.model) # GT-R

The get() method returns the value of the item with the specified key or none if the key does not exist.
This ensures that the program does not crash if the key does not exist.

Creating a class with default arguments

  
# main.py

class Car:
    def __init__(self, make="Nissan", model="GT-R"):
        self.make = make
        self.model = model

        my_car = Car()
        print(my_car.make) # Nissan
        print(my_car.model) # GT-R

GUI in python with tkinter

tkinter

tkinter is a python library that is used to create GUI applications.
tkinter is a built-in library and therefore we do not need to install it.
tkinter is a cross-platform library and therefore it works on Windows, Mac and Linux.
tkinter is a wrapper around the Tk GUI toolkit.

Tk GUI toolkit

Tk is a GUI toolkit that is used to create GUI applications.

Creating a window

  
# main.py
from tkinter import *

window = Tk()
window.title("My First GUI Program")
window.minsize(width=500, height=300)

# Label
my_label = Label(text="I am a Label", font=("Arial", 24, "bold"))
my_label.pack()

# Button
def button_clicked():
    my_label.config(text="Button got clicked")

button = Button(text="Click Me", command=button_clicked)
button.pack()

window.mainloop() # keep the window on the screen

The Label widget is used to display text on the screen.
The Button widget is used to create a button.
The command parameter is used to specify the function that will be called when the button is clicked.
The pack() method is used to display the widget on the screen.
The mainloop() method is used to keep the window on the screen.
The config() method is used to change the text of the label.

Other widgets

Entry widget: used to create a text entry box.
Text widget: used to create a multi-line text entry box.
Spinbox widget: used to create a spinbox.
Scale widget: used to create a scale.
Checkbutton widget: used to create a checkbutton.
Radiobutton widget: used to create a radiobutton.
Listbox widget: used to create a listbox.
Frame widget: used to create a frame.
Canvas widget: used to create a canvas.
Menu widget: used to create a menu.
Message widget: used to create a message.
LabelFrame widget: used to create a label frame.
PanedWindow widget: used to create a paned window.
tkMessageBox widget: used to display message boxes.
tkFileDialog widget: used to open and save files.

  
# main.py
from tkinter import *

window = Tk()
window.title("My First GUI Program")
window.minsize(width=500, height=300)

# Label
my_label = Label(text="I am a Label", font=("Arial", 24, "bold"))
my_label.pack()

# Button
def button_clicked():
    my_label.config(text="Button got clicked")

button = Button(text="Click Me", command=button_clicked)
button.pack()

# Entry
input = Entry(width=10)
input.pack()

# Text
text = Text(height=5, width=30)
text.pack()

# Spinbox
def spinbox_used():
    print(spinbox.get())

spinbox = Spinbox(from_=0, to=10, width=5, command=spinbox_used)
spinbox.pack()

# Scale
def scale_used(value):
    print(value)

scale = Scale(from_=0, to=100, command=scale_used)
scale.pack()

# Checkbutton
def checkbutton_used():
    print(checked_state.get())

checked_state = IntVar()
checkbutton = Checkbutton(text="Is On?", variable=checked_state, command=checkbutton_used)
checked_state.get()
checkbutton.pack()

# Radiobutton
def radio_used():
    print(radio_state.get())

radio_state = IntVar()
radiobutton1 = Radiobutton(text="Option1", value=1, variable=radio_state, command=radio_used)
radiobutton2 = Radiobutton(text="Option2", value=2, variable=radio_state, command=radio_used)
radiobutton1.pack()
radiobutton2.pack()

# Listbox
def listbox_used(event):
    print(listbox.get(listbox.curselection()))

listbox = Listbox(height=4)
fruits = ["Apple", "Pear", "Orange", "Banana"]
for item in fruits:
    listbox.insert(fruits.index(item), item)
listbox.bind("<<ListboxSelect>>", listbox_used)
listbox.pack()

# Frame
frame = Frame(height=100, width=100)
frame.pack()

# Canvas
canvas = Canvas(height=100, width=100)
canvas.pack()

# Menu
def menu_used():
    print("Menu item clicked")

menu = Menu()
menu.add_command(label="Item 1", command=menu_used)
menu.add_command(label="Item 2", command=menu_used)
menu.add_command(label="Item 3", command=menu_used)
menu.add_command(label="Item 4", command=menu_used)
menu.add_command(label="Item 5", command=menu_used)
menu.add_command(label="Item 6", command=menu_used)
menu.add_command(label="Item 7", command=menu_used)
menu.add_command(label="Item 8", command=menu_used)

window.config(menu=menu)

# Message
message = Message(text="This is a message")
message.pack()

# LabelFrame
labelframe = LabelFrame(text="This is a label frame")
labelframe.pack()

# PanedWindow
panedwindow = PanedWindow(orient=VERTICAL)
panedwindow.pack(fill=BOTH, expand=True)

label1 = Label(panedwindow, text="Label1")
label1.pack()

panedwindow.add(label1)

label2 = Label(panedwindow, text="Label2")
panedwindow.add(label2)


window.mainloop() # keep the window on the screen

More information about tkinter can be found in the python docs using this link.

Pack, Grid and Place

Pack, Grid and Place are the three layout managers in tkinter.

Pack

The pack() method is used to display the widget on the screen.
It packs the widgets in a block. Either horizontally or vertically.
It is the easiest to use but it is not the most precise.

Place

The place() method is used to display the widget on the screen.
It packs the widgets in a specific position using x and y coordinates.
It is the most precise but it is not the easiest to use.
It is not responsive.

  
 label.place(x=0, y=0)

Grid

The grid() method is used to display the widget on the screen.
It packs the widgets in a grid of rows and columns.
It is the best to use.
It is responsive.

  
label.grid(column=0, row=0) # label will be placed in the first column and the first row

label.grid(column=1, row=0) # label will be placed in the second column and the first row

The columnspan parameter is used to specify the number of columns the widget will span.
The rowspan parameter is used to specify the number of rows the widget will span.

  
label.grid(column=0, row=0, columnspan=2) # label will be placed in the first column and the first row and will span two columns

label.grid(column=0, row=0, rowspan=2) # label will be placed in the first column and the first row and will span two rows

When we use the grid() method, we do not need to use the pack() method.
They are incompatible with each other.

Padding

The padx parameter is used to specify the padding on the left and right of the widget.
The pady parameter is used to specify the padding on the top and bottom of the widget.

  
label.config(padx=10, pady=10)

Mile to Km converter

  
from tkinter import *


def miles_kilometers():
    miles = float(text_input.get())
    km = miles * 1.609
    km_result_label.config(text=f"{km}")
    # user_input = text_input.get()
    # km_result_label.config(text=user_input)
    # km_result_label.config(text=float(user_input) * 1.609)


window = Tk()
window.title("Mile to Km Converter")

window.minsize(width=300, height=100)
window.config(padx=20, pady=20)

# Label
equals_label = Label(text="is equal to", font=("Arial", 24, "bold"))
equals_label.grid(column=0, row=1)

# Label
km_result_label = Label(text="0", font=("Arial", 24, "bold"))
km_result_label.grid(column=1, row=1)

# Label
miles_label = Label(text="Miles", font=("Arial", 24, "bold"))
miles_label.grid(column=2, row=0)

# Label
kilometer_label = Label(text="Km", font=("Arial", 24, "bold"))
kilometer_label.grid(column=2, row=1)

# Entry
text_input = Entry(width=10)
text_input.grid(column=1, row=0)

# Button


button = Button(text="Calculate", command=miles_kilometers)
button.grid(column=1, row=2)

window.mainloop()

Python Tutorial, Day 27

This post is licensed under CC BY 4.0 by the author.

Day 27

Optional and defualt arguments in functions

Optional arguments

Default arguments

Unlimited positional arguments

*args

**kwargs

Creating a class with optional arguments

Creating a class with default arguments

GUI in python with tkinter

tkinter

Tk GUI toolkit

Creating a window

Other widgets

Pack, Grid and Place

Pack

Place

Grid

Padding

Mile to Km converter

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`*args`

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