DEV Community: chrisMurimi

Py3 101: Getting started with python3.

chrisMurimi — Sun, 17 Oct 2021 21:55:37 +0000

Python.

Python is an interpreted high-level general-purpose programming language. Its design philosophy emphasizes code readability with its use of significant indentation. Its language constructs as well as its object-oriented approach aim to help programmers write clear, logical code for small and large-scale projects.

Why python.

It is very simple to use and implement.
It is open source and has a very big community of developers.
Object-oriented and functional programming.
A lot of applications.

Installing python.

The installation procedure involves downloading the official Python .exe installer and running it on your system.
The version you need depends on what you want to do in Python.
Open your web browser and navigate to the Downloads for Windows section of the official Python website.
Search for your desired version of Python. At the time of publishing this article, the latest Python 3 release is version 3.10.0, while the latest Python 2 release is version 2.7.16.
Select a link to download either the Windows x86-64 executable installer or Windows x86 executable installer.
.

Run the Python Installer once downloaded.
Make sure you select the Install launcher for all users and Add Python 3.7 to PATH checkboxes. The latter places the interpreter in the execution path. .
Select Install Now – the recommended installation options.
.

For all recent versions of Python, the recommended installation options include Pip and IDLE. Older versions might not include such additional features.
The next dialog will prompt you to select whether to Disable path length limit. Choosing this option will allow Python to bypass the 260-character MAX_PATH limit. Effectively, it will enable Python to use long path names.

Checking if python and pip was installed.

Pip is a powerful package management system for Python software packages. Thus, make sure that you have it installed.

To verify whether Pip was installed:

Open the Start menu and type "cmd."
Select the Command Prompt application.
Enter pip -V in the console. If Pip was installed successfully, you should see the following output:

pip -v

Build your first website with flask!

chrisMurimi — Fri, 27 Aug 2021 19:48:48 +0000

In this tutorial, we'll be creating a complete login and registration system with Python Flask and MySQL.

Python is currently taking the web development scene by storm, growing consistently every year. It's easy to get started with Python and doesn't require as many dependencies that you need to download separately.

To get started with the project will set up the required packages for our project.

mkdir flaskproject

use the above command to create your project directory that will hold your project files.
Then navigate to the directory and create your python project file.
navigating to the directory we have created for the project

cd flaskproject

creating our python project

touch flaskweb.py

we will also create a folder named templates that will hold our html files and another file named static that will hold the css files.

we will create our html files here

mkdir templates

we will create our css files here

mkdir static

We will then install a virtual environment in our flaskproject folder. Python virtual environments help decouple and isolate versions of Python and associated pip packages. This allows end-users to install and manage their own set of packages that are independent of those provided by the system. Run the following command on you command prompt.

pip install virtualenv

we will then create a virtual environment for our project.

virtualenv dev

we will then start the virtual environment.

source dev/Scripts/activate

To be able to use flask we need to install it to our project. Using pip on your command prompt install flask.

pip install flask

we are now set to start the project. Open the project in your favorite IDE. For my case I love vscode. Add to open my project on my command prompt I can run the following command.

code flaskweb.py

We then build the very basic flask app and run to test if everything is working perfect.

from flask import  Flask

app = Flask(__name__)

@app.route("/")
def regiter():

    return <h1>my first flask project</h1>


if __name__ == "__main__":
    app.run(debug=True)

If every thing is working perfectly, create your html and css files. Go to the template folder and create and create 'login.html', 'layout.html', and 'home.html' files. Then open the static folder and create a file named 'style.css'. Note you can open the folder in the vscode and add the files from there.

We will then create functions with routes, and render our html files.

from flask import Flask, render_template, request, url_for, session

app = Flask(__name__)

@app.route("/")
def home():
    #our code will co here
    return render_template('home.html')

@app.route("/login")
def login():
    #our code will co here
    return render_template('login.html')

@app.route("/logout")
def logout():
    #our code will co here
    return redirect(url_for('login'))

@app.route("/register")
def register():
    #our code will co here
    return redirect('register.html')


if __name__ == "__main__":
    app.run(debug=True)

We are now going d design our web page using html and css. We will first create our layout page that will hold the similar content for all our html files to reduce redundancy.

<!DOCTYPE html>
<html>
    <head>

         {% block title %}
        <!-- we are using jinja templates to create a block where code from other html files will be passed-->
        {% endblock title %}

        <link rel="stylesheet" href="{{url_for('static', filename='login.css')}}">
    </head>


    <body>
    {% block body%}


    {%endblock body%}
    </body>
</html>

We will then create login and register forms in our login.html file.

{% extends 'layout.html' %}
{% block title%}
<title>
   {%if title%} 
        {{title}}
    {% else%}
        login
    {% endif %}
    </title>




{%endblock title%}

{% block body%}
<div class="login-wrap">
    <div class="login-html">
        <input id="tab-1" type="radio" name="tab" class="sign-in" checked><label for="tab-1" class="tab">Sign In</label>
        <input id="tab-2" type="radio" name="tab" class="sign-up"><label for="tab-2" class="tab">Sign Up</label>
        <div class="login-form">
            <div class="sign-in-htm">


                <form action="{{ url_for('login') }}" method="post" >
                    <div class="group">
                        <label for="user" class="label">Username</label>
                        <input id="user" type="text" class="input" name="Username">
                    </div>
                    <div class="group">
                        <label for="pass" class="label">Password</label>
                        <input id="pass" type="password" class="input" data-type="password" name="password">
                    </div>
                    <div class="group">
                        <input id="check" type="checkbox" class="check" checked>
                        <label for="check"><span class="icon"></span> Keep me Signed in</label>
                    </div>
                    <div class="msg">{{ msg }}</div>
                    <div class="group">
                        <input type="submit" class="button" value="Sign In">
                    </div>
                </form>


                <div class="hr"></div>
                <div class="foot-lnk">
                    <a href="#forgot">Forgot Password?</a>
                </div>
            </div>
            <div class="sign-up-htm">


            <form action="{{ url_for('register') }}" method="post">
                    <div class="group">
                        <label for="user" class="label" name="username">Username</label>
                        <input id="user" type="text" class="input">
                    </div>
                    <div class="group">
                        <label for="pass" class="label" name="password">Password</label>
                        <input id="pass" type="password" class="input" data-type="password">
                    </div>
                    <div class="group">
                        <label for="pass" class="label" name="retry_password">Repeat Password</label>
                        <input id="pass" type="password" class="input" data-type="password">
                    </div>
                    <div class="group">
                        <label for="pass" class="label" name="email">Email Address</label>
                        <input id="pass" type="text" class="input">
                    </div>
                    <div class="msg">{{ msg }}</div>
                    <div class="group">
                        <input type="submit" class="button" value="Sign Up">
                    </div>
            </form>


                <div class="hr"></div>
                <div class="foot-lnk">
                    <label for="tab-1">Already Member?</a>
                </div>
            </div>
        </div>
    </div>



</div>

{%endblock body%}

We will then create our home page.

{% extends 'layout.html' %}
{% block title%}
<title>
   {%if title%} 
        {{title}}
    {% else%}
        home
    {% endif %}
    </title>
{%endblock title%}

{% block body%}

<h2>Home Page</h2>
<p>Welcome back, {{ username }}!</p>

{%endblock body%}

The we are going to add content in our style.css file in our static folder.

body{
    margin:0;
    background:url(../images/loginbackground.jpg) no-repeat center;
    font:600 16px/18px 'Open Sans',sans-serif;
    padding: 0;
}
*,:after,:before{box-sizing:border-box}
.clearfix:after,.clearfix:before{content:'';display:table}
.clearfix:after{clear:both;display:block}
a{color:inherit;text-decoration:none}

.login-wrap{
    width:100%;
    margin:auto;
    max-width:525px;
    min-height:670px;
    position:relative;
    background:url(https://raw.githubusercontent.com/khadkamhn/day-01-login-form/master/img/bg.jpg) no-repeat center;
    box-shadow:0 12px 15px 0 rgba(0,0,0,.24),0 17px 50px 0 rgba(0,0,0,.19);
}
.login-html{
    width:100%;
    height:100%;
    position:absolute;
    padding:90px 70px 50px 70px;
    background:rgba(40,57,101,.9);
}
.login-html .sign-in-htm,
.login-html .sign-up-htm{
    top:0;
    left:0;
    right:0;
    bottom:0;
    position:absolute;
    transform:rotateY(180deg);
    backface-visibility:hidden;
    transition:all .4s linear;
}
.login-html .sign-in,
.login-html .sign-up,
.login-form .group .check{
    display:none;
}
.login-html .tab,
.login-form .group .label,
.login-form .group .button{
    text-transform:uppercase;
}
.login-html .tab{
    font-size:22px;
    margin-right:15px;
    padding-bottom:5px;
    margin:0 15px 10px 0;
    display:inline-block;
    border-bottom:2px solid transparent;
}
.login-html .sign-in:checked + .tab,
.login-html .sign-up:checked + .tab{
    color:#fff;
    border-color:#1161ee;
}
.login-form{
    min-height:345px;
    position:relative;
    perspective:1000px;
    transform-style:preserve-3d;
}
.login-form .group{
    margin-bottom:15px;
}
.login-form .group .label,
.login-form .group .input,
.login-form .group .button{
    width:100%;
    color:#fff;
    display:block;
}
.login-form .group .input,
.login-form .group .button{
    border:none;
    padding:15px 20px;
    border-radius:25px;
    background:rgba(255,255,255,.1);
}
.login-form .group input[data-type="password"]{
    text-decoration:circle;
    -webkit-text-security:circle;
}
.login-form .group .label{
    color:#aaa;
    font-size:12px;
}
.login-form .group .button{
    background:#1161ee;
}
.login-form .group label .icon{
    width:15px;
    height:15px;
    border-radius:2px;
    position:relative;
    display:inline-block;
    background:rgba(255,255,255,.1);
}
.login-form .group label .icon:before,
.login-form .group label .icon:after{
    content:'';
    width:10px;
    height:2px;
    background:#fff;
    position:absolute;
    transition:all .2s ease-in-out 0s;
}
.login-form .group label .icon:before{
    left:3px;
    width:5px;
    bottom:6px;
    transform:scale(0) rotate(0);
}
.login-form .group label .icon:after{
    top:6px;
    right:0;
    transform:scale(0) rotate(0);
}
.login-form .group .check:checked + label{
    color:#fff;
}
.login-form .group .check:checked + label .icon{
    background:#1161ee;
}
.login-form .group .check:checked + label .icon:before{
    transform:scale(1) rotate(45deg);
}
.login-form .group .check:checked + label .icon:after{
    transform:scale(1) rotate(-45deg);
}
.login-html .sign-in:checked + .tab + .sign-up + .tab + .login-form .sign-in-htm{
    transform:rotate(0);
}
.login-html .sign-up:checked + .tab + .login-form .sign-up-htm{
    transform:rotate(0);
}

.hr{
    height:2px;
    margin:60px 0 50px 0;
    background:rgba(255,255,255,.2);
}
.foot-lnk{
    text-align:center;
}

What remains now is getting data from our html forms. But before we do that we have to connect our application with a database. In this case we are using mysql database.
.
When your mySQL is set, create a new database with your favorite name.
Then use the following sql code to create a table in your database with the given values

CREATE TABLE IF NOT EXISTS `users` (
    `id` int(11) NOT NULL AUTO_INCREMENT,
    `username` varchar(50) NOT NULL,
    `password` varchar(255) NOT NULL,
    `email` varchar(100) NOT NULL,
    PRIMARY KEY (`id`)
) ```




We will then link the database with our project. To facilatate this we have to install pymysql module that will help us in the connection. Open your command prompt and use pip to install the module.


```cmd
pip install pymysql

we will then move to our flaskweb.py file and import the module.

from flask import Flask, render_template, request, url_for, session
import pymysql

Using the module we will then create a connection with our database.

from flask import Flask, render_template, request, url_for, session
import pymysql

pp = Flask(__name__)


# database connection details 
# Intializing MySQL
connection = pymysql.connect(host='localhost', password='', user='root', database='luxproject')

We will then retrive data from our html forms using post method we used to send the data to our route.

@app.route("/register", methods=['POST', 'GET'])
def regiter():
    if request.method == "POST":
        username = request.form['username']
        phone = request.form['phone']
        password = request.form['password']

We will then check the data input by the user, validate if it meet our standard and send it to our data base.

@app.route('/register' , methods=['GET', 'POST'])
def register():
    msg=''
    # Check if "username", "password" and "email" POST requests exist (user submitted form)
    if request.method == 'POST' and 'username' in request.form and 'password' in request.form and 'email' in request.form:
        # Create variables for easy access
        username = request.form['username']
        password = request.form['password']
        email = request.form['email']
        # Show registration form with message (if any)
        cursor = connection.cursor()
        cursor.execute('SELECT * FROM users WHERE username = {}'.format(username,))
        account = cursor.fetchone()
        # If account exists show error and validation checks
        if account:
            msg = 'Account already exists!'
        elif not re.match(r'[^@]+@[^@]+\.[^@]+', email):
            msg = 'Invalid email address!'
        elif not re.match(r'[A-Za-z0-9]+', username):
            msg = 'Username must contain only characters and numbers!'
        elif not username or not password or not email:
            msg = 'Please fill out the form!'
        else:
            # Account doesnt exists and the form data is valid, now insert new account into accounts table
            cursor.execute('INSERT INTO users VALUES (NULL, %s, %s, %s)', (username, password, email,))
            connection.commit()
            msg = 'You have successfully registered!'
    elif request.method == 'POST':
        # Form is empty... (no POST data)
        msg = 'Please fill out the form!'



    return render_template('login.html', msg=msg)

We will also create our login session. Here we will get user input and compare with the data in our database, if user exist we will let him in.

@app.route('/login', methods=['GET', 'POST'])
def login():
    msg=''
     # Check if "username" and "password" POST requests exist (user submitted form)
    if request.method == 'POST' and 'username' in request.form and 'password' in request.form:
        # Create variables for easy access
        username = request.form['username']
        password = request.form['password']
         # Check if account exists using MySQL
        cursor = connection.cursor()
        cursor.execute('SELECT * FROM users WHERE username = %s AND password = %s', (username, password,))

        # Fetch one record and return result
        account = cursor.fetchone()

     # If account exists in accounts table in out database
        if account:
            # Create session data, we can access this data in other routes
            session['loggedin'] = True
            session['id'] = account['id']
            session['username'] = account['username']
            # Redirect to home pag(
            return render_template('home.html')
        else:
            # Account doesnt exist or username/password incorrect
            msg = 'Incorrect username/password!'

    return render_template('login.html', msg=msg)

We will also create the home and the logout functions.
Home function

def home():
    # Check if user is loggedin
    if 'loggedin' in session:
        # User is loggedin show them the home page
        return render_template('home.html', username=session['username'])
    # User is not loggedin redirect to login page
    return redirect(url_for('login'))

logout function

@app.route('/pythonlogin/logout')
def logout():
    # Remove session data, this will log the user out
   session.pop('loggedin', None)
   session.pop('id', None)
   session.pop('username', None)
   # Redirect to login page
   return redirect(url_for('login'))

Now our flaskweb.py file should look as follows.

import re
from flask import Flask, render_template, request, url_for, session
import pymysql
from werkzeug.utils import redirect


app = Flask(__name__)


# database connection details 
# Intializing MySQL
connection = pymysql.connect(host='localhost', password='', user='root', database='luxproject')


@app.route('/')
@app.route('/home')
def home():
    # Check if user is loggedin
    if 'loggedin' in session:
        # User is loggedin show them the home page
        return render_template('home.html', username=session['username'])
    # User is not loggedin redirect to login page
    return redirect(url_for('login'))


@app.route('/login', methods=['GET', 'POST'])
def login():
    msg=''
     # Check if "username" and "password" POST requests exist (user submitted form)
    if request.method == 'POST' and 'username' in request.form and 'password' in request.form:
        # Create variables for easy access
        username = request.form['username']
        password = request.form['password']
         # Check if account exists using MySQL
        cursor = connection.cursor()
        cursor.execute('SELECT * FROM users WHERE username = %s AND password = %s', (username, password,))

        # Fetch one record and return result
        account = cursor.fetchone()

     # If account exists in accounts table in out database
        if account:
            # Create session data, we can access this data in other routes
            session['loggedin'] = True
            session['id'] = account['id']
            session['username'] = account['username']
            # Redirect to home pag(
            return render_template('home.html')
        else:
            # Account doesnt exist or username/password incorrect
            msg = 'Incorrect username/password!'

    return render_template('login.html', msg=msg)



@app.route('/pythonlogin/logout')
def logout():
    # Remove session data, this will log the user out
   session.pop('loggedin', None)
   session.pop('id', None)
   session.pop('username', None)
   # Redirect to login page
   return redirect(url_for('login'))


@app.route('/register' , methods=['GET', 'POST'])
def register():
    msg=''
    # Check if "username", "password" and "email" POST requests exist (user submitted form)
    if request.method == 'POST' and 'username' in request.form and 'password' in request.form and 'email' in request.form:
        # Create variables for easy access
        username = request.form['username']
        password = request.form['password']
        email = request.form['email']
        # Show registration form with message (if any)
        cursor = connection.cursor()
        cursor.execute('SELECT * FROM users WHERE username = {}'.format(username,))
        account = cursor.fetchone()
        # If account exists show error and validation checks
        if account:
            msg = 'Account already exists!'
        elif not re.match(r'[^@]+@[^@]+\.[^@]+', email):
            msg = 'Invalid email address!'
        elif not re.match(r'[A-Za-z0-9]+', username):
            msg = 'Username must contain only characters and numbers!'
        elif not username or not password or not email:
            msg = 'Please fill out the form!'
        else:
            # Account doesnt exists and the form data is valid, now insert new account into accounts table
            cursor.execute('INSERT INTO users VALUES (NULL, %s, %s, %s)', (username, password, email,))
            connection.commit()
            msg = 'You have successfully registered!'
    elif request.method == 'POST':
        # Form is empty... (no POST data)
        msg = 'Please fill out the form!'



    return render_template('login.html', msg=msg)


if __name__ == ('__main__'):
    app.run(debug=True)

Now you have developed you first flask website. Do you fill excited! . Feel free to drop your in put.

Quick start! getting started with flask, python3.

chrisMurimi — Tue, 10 Aug 2021 17:14:05 +0000

Python is a cool and beautiful programing language. It is beginner friendly, easy to learn and its syntax is very clear and concise. Python is yet powerful enough to be used by global tech giants in their products and applications. One area where Python shines is web development. Python offers many frameworks from which to choose from including bottle.py, Flask, Fast API, CherryPy, Pyramid, Django and web2py. This frameworks have been used is some of the most world applications.

What is flask.

Flask is a micro web framework written in Python. It is classified as a microframework because it does not require particular tools or libraries. It has no database abstraction layer, form validation, or any other components where pre-existing third-party libraries provide common functions. However, Flask supports extensions that can add application features as if they were implemented in Flask itself. Extensions exist for object-relational mappers, form validation, upload handling, various open authentication technologies and several common framework related tools.

Setting up Flask.

Python Virtual environment.

A virtual environment is a Python environment such that the Python interpreter, libraries and scripts installed into it are isolated from those installed in other virtual environments, and (by default) any libraries installed in a “system” Python, i.e., one which is installed as part of your operating system.
virtual environment is used to manage Python packages for different projects. Using virtual environment allows you to avoid installing Python packages globally which could break system tools or other projects.

You can install virtual environment using pip. Use this code in windows (I recommend using git bash than the windows CMD):

pip install virtualenv

Create the virtual environment.

virtualenv my_env

my_env is the name of the virtual environment we have created.

Activate the virtual environment.

source my_env\Scripts\activate

Now we have a virtual environment let install flask.

Installing flask.

Flask is easy to set up. Use pip install flask to install both Flask and all of its dependencies including the Jinja2 templating system.

pip install flask

A basic Flask app.

from flask import Flask

app = Flask(__name__)

@app.route("/")
def hello_world(self):
    return "Hello, world"

This app doesn’t do much — it just creates a website with a single route that displays “Hello, world” in the browser.

Routes in flask.

Routes in a Flask app can be created by defining a view function and associating a URL with it using the route() decorator. Routes specify how the Flask app handles requests it receives, such as what to display on the webpage at a certain URL.

@app.route("/")
def hello_world(self):
    return "Hello, world"

Flask App Object.

The Python flask module contains all the classes and functions needed for building a Flask app. The Flask class can be imported to create the main application object. It takes the name of the app as an argument.

from flask import Flask

app = Flask(__name__)

Running Flask App.

A Flask app can be run by exporting the FLASK_APP environment variable and running flask run in the terminal.

export FLASK_APP=app.py
flask run

Introduction To Python Functions

chrisMurimi — Mon, 02 Aug 2021 20:18:37 +0000

Here you learn about python functions, the component of a function, the syntax and how to write functions in python.

What is a function in Python?

Function in python is a group of related statements/ (lines of code) that performs a specific task. Functions help make the program more organized and manageable by breaking the program into smaller and modular chunks. Functions helps reduce repetition and make the code reusable.

def function_name(self):
   '''block of code in this function appear here'''
    pass

Def is a keyword and marks the start of the function.
function_name is the name to the function. A function name to uniquely identify the function. Function naming follows the same rules of writing identifiers in Python.
self is a parameter. Parameters through which we pass values to a function. They are optional. *A colon (:) to mark the end of the function header.
Statements that make the function body must have same indentation level (usually 4 spaces).
If a functions returns anything the return function is used.

def sum(num1, num2):
'''this adds two numbers'''
    return num1 + num2

The above function named sum receives two numbers as the parameters and returns the sum of the two numbers.

How to call a function in python?

A function can be called from another function, program or even the python prompt. To call a function we simply type the function name with appropriate parameters.

def sum(num1, num2):
'''this adds two numbers'''
    return num1 + num2
sum(4,5)

The return statement.

The return statement is used to exit a function and go back to the place from where it was called. This statement can contain an expression that gets evaluated and the value is returned. If there is no expression in the statement or the return statement itself is not present inside a function, then the function will return the None object.

Scope and Lifetime of variables.

Scope of a variable is the portion of a program where the variable is recognized. Parameters and variables defined inside a function are not visible from outside the function. Hence, they have a local scope.

The lifetime of a variable is the period throughout which the variable exits in the memory. The lifetime of variables inside a function is as long as the function executes.

They are destroyed once we return from the function. Hence, a function does not remember the value of a variable from its previous calls.

def sum():
    x = 10 #value inside the function
    print(x)
y = 10 #value outside the function
print(y)

In general, variables that are defined inside a function body have a local scope, and those defined outside have a global scope. That means that local variables are defined within a function block and can only be accessed inside that function, while global variables can be obtained by all functions that might be in your script.

Types of Functions in python.

There are three types of functions in Python:

Built-in functions, such as help() to ask for help, min() to get the minimum value, print() to print an object to the terminal,… You can find an overview with more of these functions here.
User-Defined Functions (UDFs), which are functions that users create to help them out; And
Anonymous functions, which are also called lambda functions because they are not declared with the standard def keyword.

How To Define A Function (User-Defined Functions).

The four steps to defining a function in Python are the following:

Use the keyword def to declare the function and follow this up with the function name.
Add parameters to the function: they should be within the parentheses of the function. End your line with a colon.
Add statements that the functions should execute. *End your function with a return statement if the function should output something. Without the return statement, your function will return an object None.

Parameters vs Arguments

Parameters are the names used when defining a function or a method, and into which arguments will be mapped. In other words, arguments are the things which are supplied to any function or method call, while the function or method code refers to the arguments by their parameter names.

Functions vs Methods

A method refers to a function which is part of a class. You access it with an instance or object of the class. A function doesn’t have this restriction: it just refers to a standalone function. This means that all methods are functions, but not all functions are methods.

def my_function():
    return "hello world" #this is a function.

class my_class:
     def my_method(self): # this is a method
            return "hello world"

#Python Basics, Python 101!

chrisMurimi — Sat, 24 Jul 2021 12:09:20 +0000

Python is an interpreted, object-oriented, high-level programming language with dynamic semantics. Python language is incredibly easy to use and learn for new beginners and newcomers. The python language is one of the most accessible programming languages available because it has simplified syntax and is not complicated, which gives more emphasis on natural language.

About Python

It is a high-level language
It is interpreted
It is both object-oriented and functional
It is portable
It is extensible and embeddable
It comes with a vast collection of libraries

Python Applications

Web Development
Game Development
Data science
Scientific and Numeric Applications
Artificial Intelligence and Machine Learning
Automation
Desktop GUI
Enterprise-level/Business Applications

Some IDEs to use in python development

Pycharm --- download here Pycharm
Anaconda --- download here Anaconda
VS code --- download here VScode
Spyder --- download here Spyder

Python syntax

The syntax of the Python programming language is the set of rules which defines how a Python program will be written.
A Python program is divided into a number of logical lines and every logical line is terminated by the token NEWLINE. A logical line is created from one or more physical lines.
A line contains only spaces, tabs, form feeds possibly a comment, is known as a blank line, and Python interpreter ignores it.
A physical line is a sequence of characters terminated by an end-of-line sequence

name = "Jane"  # this variable stores the string Jane
print("Hello", name)

Python uses whitespace (spaces and tabs) to define program blocks whereas other languages like C, C++ use braces ({}) to indicate blocks of codes for class, functions or flow control.

Python Coding Style:

Use 4 spaces per indentation and no tabs
Do not mix tabs and spaces
Tabs create confusion and it is recommended to use only spaces
Maximum line length : 79 characters which help users with a small display
Use blank lines to separate top-level function and class definitions and single blank line to separate methods definitions inside a class and larger blocks of code inside functions
When possible, put inline comments (should be complete sentences) *Use spaces around expressions and statements.

Comments in python

A comment begins with a hash character(#) which is not a part of the string literal and ends at the end of the physical line. All characters after the # character up to the end of the line are part of the comment and the Python interpreter ignores them.

name = input("enter your name")
# comment
print("hello", name)

Identifiers, keywords and literals in python.

Keyword --- Keywords are the reserved words in Python. We cannot use a keyword as a variable name, function name or any other identifier. They are used to define the syntax and structure of the Python language. All the keywords except True , False and None are in lowercase and they must be written as they are.
Identifiers --- is a name used to identify a variable, function, class, module or other object.
Literals --- is a succinct and easily visible way to write a value. There are four type of literals in python. --- String literals ("string") --- numeric literals (1,2,3...) --- Boolean literals(True, False) --- Special Literal (none)

Data types in python

String
Integer
Floats
Complex

Data structures in python

List

A list is a data structure in Python that is a mutable, or changeable, ordered sequence of elements. Each element or value that is inside of a list is called an item. Just as strings are defined as characters between quotes, lists are defined by having values between square brackets [ ].

fruits = ["mangoes", "bananas", "orange"]
print(fruits)

to add to a list we use the append function.

fruits = ["mangoes", "bananas", "orange"]
fruits.append("lemon")
print(fruits)

To remove items from a list the .remove function is used.

Tuples

Python tuples are a data structure that store an ordered sequence of values. Tuples are immutable. This means you cannot change the values in a tuple. They let you store an ordered sequence of items. For example, you may use a tuple to store a list of employee names.

fruits = ("mangoes", "bananas", "orange")
print(fruits)

Dictionaries in python.

Dictionary in Python is an ordered collection of data values, used to store data values like a map, which, unlike other Data Types that hold only a single value as an element, Dictionary holds key:value pair. Key-value is provided in the dictionary to make it more optimized.

chris = {
    "name": "Chris Murimi",
    "age": 23
}
print(chris)

Sets

Sets are used to store multiple items in a single variable. Set is one of 4 built-in data types in Python used to store collections of data, the other 3 are List, Tuple, and Dictionary, all with different qualities and usage. A set is a collection which is both unordered and unindexed.

Operators in python.

Operators are special symbols in Python that carry out arithmetic or logical computation. The value that the operator operates on is called the operand. For example: >>> 2+3 5. Here, + is the operator that performs addition.
Operators type in python:

Arithmetic operators: Arithmetic operators are used to perform mathematical operations like addition, subtraction, multiplication and division.
Relational Operators: Relational operators compares the values. It either returns True or False according to the condition.
Logical operators: Logical operators perform Logical AND, Logical OR and Logical NOT operations.
Bitwise operators: Bitwise operators acts on bits and performs bit by bit operation.
Assignment operators: Assignment operators are used to assign values to the variables.
Special operators: There are some special type of operators like- Identity operators- is and is not are the identity operators both are used to check if two values are located on the same part of the memory. Two variables that are equal does not imply that they are identical. Membership operators- in and not in are the membership operators; used to test whether a value or variable is in a sequence.
Precedence and Associativity of Operators: Operator precedence and associativity as these determine the priorities of the operator.