DEV Community: Eric Mutua

Python for Everyone: Mastering Python the right way

Eric Mutua — Fri, 04 Mar 2022 09:32:41 +0000

Well, your path to become a python guru is on track. Here we shall discuss on how to master python the right way.

THE BASICS!!

The basics of any programming language are fundamental in mastering the language as a whole.
Learning the fundamentals of python will give you the basic understanding of python. For starters, you can catch up with the basics of python programming here:
https://dev.to/am_eric/python-101-getting-started-1np2

INTERMEDIATE PYTHON

Next on track is intermediate python. Here you will get to understand data structures and algorithms and their implementation.Learn data structures and algorithms with me at
https://dev.to/am_eric/introduction-to-data-structures-and-algorithms-with-python-51fp.
Once equipped with these skills, you can now decide on your preferable track. It may be:

Web development
Data Science
Artificial Intelligence and Machine Learning
Game Development among others.

ADVANCED PYTHON

For web development, frameworks such as:

Django
Flask
Pyramid
Falcon

The most popular frameworks are Django and Flask.
Django - is a high-level Python Web framework that encourages rapid development and clean, pragmatic design.
Flask - is a lightweight python framework that provides the tools necessary to create robust web applications.
Lets take a dive into Django.

Introduction to Django

Requirements:

You should at least have some knowledge in python programming before trying out a framework.
You should have python installed in your PC.

Installation

On your cmd on windows, do
pip install django

Wait till the installation is completed.
Check the django version installed. Do
py -m django --version

Next,create a virtual environment. Do
mkvirtualenv myapp

in an instance where it throws an error -

'mkvirtualenv' is not recognized as an internal or external command,
operable program or batch file.

DO:
pip install virtualenvwrapper-win

then

mkvirtualenv myapp

Inside the virtual env:

(myapp) C:\Users\Eric>

Do:
pip install django
to install django on the virtual environment

then
django-admin startproject myproject

To be:

(myapp) C:\Users\Eric>django-admin startproject myproject

you can alter 'myproject' with the name of your preferred project.

Next, open the project on your preferred compilier.

Creating apps in myproject

Do:
python manage.py startapp myapp

(myapp) C:\Users\Eric>python manage.py startapp myapp

Creating an app would look like this:

myapp/
    __init__.py
    admin.py
    apps.py
    migrations/
        __init__.py
    models.py
    tests.py
    views.py

Getting the First Output in Django

We use the views.py to return responses to the screen.
At the views.py, do:

from django.shortcuts import render
from django.http import HttpResponse

def index(request):
    return HttpResponse(<h2>"Welcome to my first django application"</h2>)

Next step is the ####URL-routing
Create a new python file and name it urls.py

myapp/
    __init__.py
    admin.py
    apps.py
    migrations/
        __init__.py
    models.py
    tests.py
    urls.py
    views.py

Aturls.py:

from django.urls import path

from . import views

urlpatterns = [
    path('', views.index, name='index'),
]

Now run the project.

DO:
python manage.py runserver

The output will be;

Performing system checks...

System check identified no issues (0 silenced).

You have unapplied migrations; your app may not work properly until they are applied.
Run 'python manage.py migrate' to apply them.

March 01, 2022 - 15:50:53
Django version 4.0, using settings 'myapp.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.

Now that the server is running, visit http://127.0.0.1:8000/ at your web browser

Next,point the root URLconf at the myapp.urls module.
At myproject/urls.py , do;

from django.contrib import admin
from django.urls import include, path

urlpatterns = [
    path('', include('myapp.urls')),
    path('admin/', admin.site.urls),
]

The include() function allows referencing other URLconfs.

Finally, run the server again and refresh the page.

Do:
python manage.py runserver

The output 'Welcome to my first django application' should be visible from the page.

Thank You for taking time to read this article. Follow for more.

Introduction to Data Structures and Algorithms With Python.

Eric Mutua — Sun, 20 Feb 2022 20:26:49 +0000

Data Structures

Python has four inbuilt basic data structures which are:
Lists, Dictionary, Tuple and Sets.
To start with:
Lists
Lists can be used for any type of object. From numbers to string and also lists.
Lists are defined by brackets - []

numbers = [4,5,6]
print(type(numbers))

output:

<class 'list'>

Lists can also be defined by using the keyword list()

numbers = list()
numbers.append(4)
numbers.append(5)
numbers.append(6)
print(numbers)
[4, 5, 6]

There are set of built-in methods used with lists.

append() - Adds an element at the end of the list
clear() - Removes the elements of a list
copy() - Returns a copy of the list
pop() - Removes the element at the specified position
insert() - Adds an element at the specified position
reverse() - Reverses the order of the list
sort() - Sorts the list
remove - removes the first item with the specified value
count - returns the number of elements with the specified value.

Dictionary
Dictionaries referred to as hashmaps in other languages. It consists of key, value pairs. Key are unique and immutable objects.
Each key and value pair are seperated by a colon.
Dictionaries are defined by curly brackets {}.

Dict = {'name': 'Eric', 'age': 19}

There are also a set of inbuilt python dictionary methods

clear() - Removes all items from a dictionary
copy() - Returns a copy of the dictionary
get() - gets the value of the specified parameter
items() - gets all items of a dictionary in the key value format
popitem() - Removes and returns the last element in the dictionary
update() - updates the dictionary with the key-value pairs
keys() - returns a list containing the dictionary's keys
values() - returns a list of all the values in the dictionary

Tuple
A tuples is ordered and immutable.
Duplicates are allowed in tuples.
Tuples are defined with brackets () and are indexed.

mytuple = ("cat", "mouse", "cow", "chicken")

Tuples can be accessed through indexing

mytuple = ("cat", "mouse", "cow", "chicken")
print(mytuple[1])

# output:

mouse

Sets
Sets are unordered, immutable and unindexed.
Duplicates are not allowed in sets
Sets are defined with curly brackets {}

myset = {"cat", "mouse", "cow", "chicken"}

There are built-in set methods.

add() - Adds an element to the set
clear() - removes all the elements from the set
copy() - returns a copy of the set
discard() - removes the specified item
pop() - removes an element from the set
update() - updates the set with another set
remove() - removes the specified item

Algorithms

Queues
A queue is an abstract data structure that is open on both sides hence use first in first out basis FIFO.
A queue has two ends; front and rear.

The two operations involved with queues are enqueue and dequeue.
Enqueue involves inserting items in a queue while dequeue is the process of removing items.

Methods involved in queues include:
push(item) - used to insert an element to the queue.
pop(item) - used to remove an element from the queue.
get() - used to extract an element from the queue.
empty() - check whether a queue is empty or not.
full() - check whether a queue is full.

Implementation of queues using list in python

q = []
def Enqueue():
    if len(q) == size:
        print('Queue is full')
    else:
        number = input('Enter numbers-:')
        q.append(number)
        print(number,'number added to the queue')

def dequeue():
    if len(queue) == 0:
        print('queue is empty')
    else:
        del = q.pop(0)
        print('Element removed',del)

def display():
    size = input('Enter size of the queue')
    while True:
        print("Select the Operation:1.Add 2.Delete 3. Display 4. Quit")
        choice=int(input())
        if choice==1:
            Enqueue()
        elif choice==2:
            dequeue()
        elif choice==3:
            display()
        elif choice==4:
            break
        else:
            print("Invalid Choice =(")

Stacks

A stack is a linear data structure that stores items in a last-in-First-Out order.

A stack is open on one side hence a new item is added at one end and removed from that end only.

The methods involved with stacks are:
empty() - returns whether stack is empty.
size() - returns size of the stack.
top() - returns a reference to the topmost element of the stack.
push() - inserts items at the top of the stack.
pop() - Deletes the topmost element of the stack.

Implementation using list

stack = []

#append() used to push items into stack
stack.append('a')
stack.append('b')
stack.append('c')

print(stack)

#pop() removes items from stack

print(stack.pop())
print(stack.pop())
print(stack.pop())

#elements after being popped
print(stack)

Linked Lists
A linked list is a sequence of data elements which are connected via links.
Each link contains connection to another link.
Python does not have linked lists in its standard library.

The first node is also known as the HEAD. It is used as a reference to traverse the list.
The last node points to NULL.

Types of Linked Lists

Singly linked list - traversed in forward direction
Doubly linked list - traversed in forward and back directions
Circular singly linked list - the last element contains link to the first element as next
Circular Doubly linked list - the last element contains link to the first element as next and the first element contains link of the last element as previous.


Implementation of nodes using classes

class Node:
  #constructor to create a new node
  def __init__(self, data):
    self.data = data
    self.next = None


class LinkedList:
  #constructor to create an empty LinkedList
  def __init__(self):
    self.head = None

# create an empty LinkedList                 
MyList = LinkedList()

#Add first node.
first = Node(1)
#linking with head node
MyList.head = first

#Add second node.
second = Node(2)
#linking with first node
first.next = second

#Add third node.
third = Node(3)
#linking with second node
second.next = third

Thank you for reading this article. I hope it was of great assistance understanding data structures and algorithms with python.

PYTHON 101; GETTING STARTED

Eric Mutua — Wed, 09 Feb 2022 09:40:09 +0000

WHAT IS PYTHON

First released in 1991 and created by Guido van Rossum, python is an interpreted, high-level and general-purpose programming language.

GETTING STARTED

Python Installation

You can download the various versions of python through your preferred browser(preferred versions 3.6+).

Clicking on download will download python.
Click on the..exe file to set up python in your computer

Writing the First Code
Open the Command Prompt and type python

You will be able to access Python.

print(Hello World)

FUNDAMENTALS OF PYTHON

Here we get to know Python;

Variables
Strings and Comments
Operators
Lists
Dictionaries
Sets
Functions

Variables

A variable is a storage location (Identified by the memory adress) paired with an associated symbolic name(an identifier), which contains some known or unknown quantity of information refered to as a value.

name= eric
age= 19
name and age are variables

Strings and Comments

# is used to convert a string to a comment

print("hello world")
#print ("Hello world")

Operators

There are different types of operators

Boolean
Boolean values are two which are True or False
Comprison
Comparison operators are

Equal (==)
Not equal (!=)
Greater than (>)
Less than (<)
Greater or equal to (>=)
Less than or equal to (<=)
Logical and or not

Lists

In lists, characters are enclosed in brackets [].

Dictionaries

Items are stored in a key, value pair in a dictionary.
Dictionaries are defined using curly braces {} and are ordered.

Sets

Sets are defined using curly braces {} and are unordered.

ages = {19,20,21,22,23}
ages
{19,20,21,22,23}

Functions

A function is a block of code that runs when it is called.
a function is defined with the def keyword.

def name():
    print('eric')

name()
eric

Here, name() is calls the function to execute.

In Conclusion, that was an overview of getting strarted with python programming for beginners. As part of LUX Academy,i am happy to be here.