Python Contact Management with JSON

 
 import json  
 import os  
 
 CONTACTS_FILE = "contacts.json"  
 
 def load_contacts():  
   if not os.path.exists(CONTACTS_FILE):  
     return[]  
   try:  
     with open(CONTACTS_FILE, 'r') as file:  
       return json.load(file)  
   except (json.JSONDecodeError, IOError):  
     print("Error reading contacts file. Starting with an empty list")  
     return [] 
     
 def save_contacts(contacts):  
   try:   
     with open(CONTACTS_FILE, 'w') as file:  
       json.dump(contacts, file, indent=4)  
     print("Contact saved successfully")  
   except IOError as e:  
     print(f"Error saving contacts: {e}")  
     
 def create_contact(contacts):  
   print("\n--- Add New Contact ---")  
   name = input("Enter name : ").strip()  
   if not name:  
     print("Name cannot be empty.")  
     return  
   location = input("Enter location : ").strip()  
   if not location:  
     print("Location cannot be empty.")  
     return  
   new_contact= {  
     'name': name,  
     'location': location  
   }  
   contacts.append(new_contact)  
   save_contacts(contacts)  
   print(f"Contact '{name}' added successfully")  
   
 def read_contacts(contacts):  
   print("\n-- All Contacts --")  
   if not contacts:  
     print("No contacts found")  
     return  
   for index, contact in enumerate(contacts, start=1):  
     print(f"{index}. Name: {contact['name']}, Location: {contact['location']}")  
     
 def main():  
   contacts = load_contacts()  
   # read_contacts()  
   while True:  
     print("\n== Contact Management System ==")  
     print("1. Add Contact")  
     print("2 View Contacts")  
     print("3. Exit")  
     choice = input("Enter your choice (1-3): ").strip()  
     print(choice)  
     if choice == '1':  
       create_contact(contacts)  
     elif choice == '2':  
       read_contacts(contacts)  
     elif choice == '3':  
       print("Exiting Contact Management System. Goodbye")  
       break  
     else:  
       print("Invalid choice. Please enter a number between 1 and 3")  
       
 if __name__=="__main__":  
   main()  

Configuring Swagger in Web API 10

Web API 10 doesn't come with Swagger support. It can be added by adding a reference to Swashbucke.AspNetCore, Adding SwaggerGen to Service, use it in the middleware and making alterations in launchSettins.json.

Program.cs

builder.Services.AddEndpointsApiExplorer();

builder.Services.AddSwaggerGen();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

launchSettings.json

"http": {
  ...
  "launchBrowser": true,
  "launchUrl": "swagger",
  "applicationUrl": "http://localhost:5294",
  ...
  }

.Net 9 with Angular 19

Visual Studio provides a project template for working with Angular and .Net Core.

It creates a solution with separate Web Api and Angular projects.

WeatherForecast Web API's data is consumed by the Angular Component. 

Converting Module based project to Stand alone

The Angular project still uses Modules instead of Stand Alone Component.

ng g @angular/core:standalone

ng generate @angular/core:standalone schematics can be used to convert Module based Angular project to Stand alone.

.Net 8 MVC

.Net Model View Controller (MVC) is a Server Side Web Application Technology. It Comprises of Model, which is the object oriented representation of data by way of POCO classes. View represents the user interface. Controller represents the user Interaction. There are other alternatives like Razor Pages for creating Server Side .Net applications. Mastering MVC will go a long way in learning other technologies like .Net Web API(with Controllers).

.Net MVC application can be developed either using Visual Studio, Visual Studio Code C# Dev Kit or .Net CLI. I am going develop MVC using Visual Studio.

Convention Over Configuration

Convention over Configuration is a software design pattern which denotes following certain conventions to avoid a lot of configurations. MVC used Convention Over Configuration when it comes to Controllers and Views. Controllers All Controllers should be inside the controllers folder. Controllers should have a Controller suffix. HomeController - Controller name is actually Home. View All the views should be inside the Views folder. There will be a folder in the Views folder corresponding the the Controller. Eg: There will be a Home folder inside the Views Folder for holding the views corresponding to Home Controllers action Methods.

MVC Project Structure

Controllers

User Interaction happens through Controllers. Controllers comprises of Action Methods.

 using Microsoft.AspNetCore.Mvc;  
 namespace MVCShalvin.Controllers  
 {  
   public class HomeController : Controller  
   {  
     public IActionResult Index()  
     {  
       return View();  
     }  
     public IActionResult Privacy()  
     {  
       return View();  
     }     
   }  
 }  

Here there are Index and Privacy Action Methods which returns View.

View

MVC View are created using Razor syntax. Razor comprises of C# code and HTML templates. Razor files have .cshtml extension Inside the Views Folder there is a Shared folder which contains Layout.cshtml which contains the common look and feel for the pages like Header, Footer etc. @RenderBody() section within the Layout.cshtml contains the View specific UI.

Models

 namespace MVCShalvin.Models  
 {  
   public class Faculty  
   {  
     public string Name { get; set; }  
     public string Specialization { get; set; }  
   }  
 }  

Passing data from Controller to View

 using Microsoft.AspNetCore.Mvc;  
 using MVCShalvin.Models;  
 namespace MVCShalvin.Controllers  
 {  
   public class HomeController : Controller  
   {  
     Faculty faculty = new Faculty  
     {  
       Name = "Shalvin P D",  
       Specialization = ".Net"  
     };  
     public IActionResult Index()  
     {  
       return View(faculty);  
     }  
   }  
 }  

Here the faculty object is passed as a parameter to View.

Index.cshtml

 @model MVCShalvin.Models.Faculty  
 <div>Hello @Model.Name specializing in @Model.Specialization</div>  

C# 12

C# is a popular cross platform programming language used to creating wide ranging of applications like Web, Desktop, or Mobile. 

 

You can create a C# application using wide range of options like  Visual Studio or  Visual Studio Code.

Here I am concentrating on .Net CLI with Visual Studio Code.

.Net CLI

.Net CLI (Command Line Interface) can be used to create and build .Net application.

 

As mentioned in the options dotnet -h or dotnet --help can be use to display .net help.

Creating a .Net CLI Console project.

 dotnet new console -o HelloConsole  

 

This command creates a console application within a folder called HelloConsole inside the current folder.

code . opens the current folder which comprises of the project in Visual Studio Code.

Top Level Statement

Program.cs file within project contains WriteLine method of Console class for displaying a message in the command prompt. 

C# follows Pascal case. Identifiers should stat with capital letter. So Console's C, WriteLine's W and L should be capital.

 Console.WriteLine("Hello Shalvin P D");  

Memory Variable

 string name = "Shalvin P D";  
 Console.WriteLine("Hello, {0}", name);  

Interpolation

 string name = "Shalvin";  
 Console.WriteLine($"Hello {name}");  

Multiple Memory Variable

 string name = "Shalvin";  
 string location = "Kochi";  
 Console.WriteLine($"Hello {name}, located at {location}.");  

Memory Variable Console.ReadLine

 string name;  
 Console.WriteLine("Enter your Name: ");  
 name = Console.ReadLine();  
 Console.WriteLine($"Hello {name}");  

Multiple String Memory Variables

 string name, location;  
 Console.WriteLine("Enter your Name: ");  
 name = Console.ReadLine();  
 Console.WriteLine("Enter your Location: ");  
 location = Console.ReadLine();  
 Console.WriteLine($"Hello {name}, located at {location}.");  

Integer Memory Variable

 int i, j, res;  
 i = 23;  
 j = 45;  
 res = i + j;  
 Console.WriteLine(res);  

Int32.Parse (Simple Calculator)

 int i, j, res;  
 Console.WriteLine("Enter Value 1: ");  
   i = Int32.Parse(Console.ReadLine());  
 Console.WriteLine("Enter Value 2: ");  
   j = Int32.Parse(Console.ReadLine());  
 res = i + j;  
 Console.WriteLine(res);  

If Statement

 string city;  
 Console.WriteLine("Enter the Name of the City: ");  
 city = Console.ReadLine();  
 if (city == "Kochi")  
 {  
   Console.WriteLine("Industrial Capital of Kerala");  
 }  

If else

 string city;  
 Console.WriteLine("Enter the Name of the City: ");  
 city = Console.ReadLine();  
 if (city == "Kochi")  
 {  
   Console.WriteLine("Industrial Capital of Kerala");  
 }  
 else  
 {  
   Console.WriteLine("I don't know");  
 }  

Multiple else if

 string city;  
 Console.WriteLine("Enter the Name of the City: ");  
 city = Console.ReadLine();  
 if (city == "Kochi")  
 {  
   Console.WriteLine("Industrial Capital of Kerala");  
 }  
 else if (city == "Trichur")  
 {  
   Console.WriteLine("Cultural Capital of India");  
 }  
 else if (city == "Trivandrum")  
 {  
   Console.WriteLine("Capital of Kerala");  
 }  
 else  
 {  
   Console.WriteLine("I don't know");  
 }  

Angular : Part 1 Getting Started with StackBlitz

Angular is a Single Page Application (SPA) framework from Google. Single Page Application is a web application that works entirely in the client side creating a rich user experience like that of Desktop application. Gmail is an example of SPA.

Setting a local development Angular requires installing NodeJS.

Easiest way to get started with Angular is Stackblitz. Stackblitz is an online editor.

For starting a new Angular project click the START A NEW APP option. 

Python 2 Functions

Functions

 def hello():  
   print("Hello functions")  
 hello()  

Functions with Parameters

 def add(i, j):  
   return i + j  
 print(add(12, 23))  

Exception Handling

 try:  
   i = int(input("Enter value 1 : "))  
   j = int(input("Enter value 2 : "))  
   res = i / j  
   print(res)  
 except ValueError:  
   print("Invalid Input")  
 except ZeroDivisionError:  
   print("Cannot divide by zero")  

 def divide():  
   try:  
     i = int(input("Enter value 1 : "))  
     j = int(input("Enter value 2 : "))   
     res = i / j  
     print(res)  
   except ValueError:  
     print("Invalid Input")  
   except ZeroDivisionError:  
     print("Cannot divide by zero")  


 divide()  

Python

print

 print("Hello Python")  

Memory Variable

 name = "Shalvin P D"  
 print("Hello ", name)  

Multiple assignments

 name, passion = "Shalvin", "IT"  
 print(f"{name} - {passion}")  

input

 name = input("Enter your name : ")  
 print("Hello ", name)  

int()

 i = int(input("Enter value 1 : "))  
 j = int(input("Enter value 2 : "))  
 res = i + j  
 print(res)  

float()

 i = float(input("Enter value 1 : "))  
 j = float(input("Enter value 2 : "))  
 res = i + j  
 print(res)  

Lists

Lists are mutable collection.

 technologies = [".Net", "Python", "Angular"]  
 for tech in technologies:  
   print(tech)  

Lists append()

 technologies = [".Net", "Python", "Angular"]  
 technologies.append("C#")  
 for tech in technologies:  
   print(tech)  

Lists remove()

 technologies = [".Net", "Python", "Angular", "C#", "PHP"]  
 technologies.remove("PHP")  
 for tech in technologies:  
   print(tech)  

Lists Concatenation

technologies1 = [".Net", "Python", "Angular", "C#"]

technologies2 = ["DevOps", "Jenkins"]

technologies = technologies1 + technologies2

for tech in technologies:
    print(tech)

Tuples

Tuples are Immutable Collection.

 contacts = ("Shalvin", "Arun")  
 for contact in contacts:  
   print(contact)  

Dictionary

Dictionary is a collection of key value pairs.

 contact = {"name" : "Shalvin", "location": "Kochi"}  
 print(contact)  
 print(contact["name"])  
 print(f'{contact["name"]} : {contact["location"]}')  

List of Dictionaries

 contacts = [{"name" : "Shalvin", "location": "Kochi"},  
       {"name": "Praseed", "location": "UK"}]  
 print(contacts)  
 first_contact = contacts[0]  
 print(first_contact)  
 print(f"{first_contact['name']} - {first_contact['location']}")  
 

 print("Listing all contacts")  
 for contact in contacts:  
   print(f"{contact['name']} - {contact['location']}")