{
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  "metadata": {
    "colab": {
      "name": "Python Variables.ipynb",
      "provenance": [],
      "authorship_tag": "ABX9TyNaHyzT8vEu+M5zbjDt87/W",
      "include_colab_link": true
    },
    "kernelspec": {
      "name": "python3",
      "display_name": "Python 3"
    }
  },
  "cells": [
    {
      "cell_type": "markdown",
      "metadata": {
        "id": "view-in-github",
        "colab_type": "text"
      },
      "source": [
        "<a href=\"https://colab.research.google.com/github/Tanu-N-Prabhu/Python/blob/master/Python_Variables.ipynb\" target=\"_parent\"><img src=\"https://colab.research.google.com/assets/colab-badge.svg\" alt=\"Open In Colab\"/></a>"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {
        "id": "yRgHPumxce8E",
        "colab_type": "text"
      },
      "source": [
        "# **Python Variables**\n",
        "\n",
        "![alt text](https://images.unsplash.com/photo-1484417894907-623942c8ee29?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=889&q=80)\n",
        "\n",
        "\n",
        "In programming languages like C/C++, every time a variable is declared simultaneously a memory would be allocated this would allocation would completely depend on the variable type. Therefore, the programmers must specify the variable type while creating a variable. But luckily in Python, you don’t have to do that. Python doesn’t have a variable type declaration. Like pointers in C, variables in Python don’t store values legitimately; they work with references highlighting objects in memory.\n",
        "\n",
        "## **Variables**\n",
        "\n",
        "A variable is more likely a ***container*** to store the values. Now the values to be stored depends on the programmer whether to use integer, float, string or **[etc](https://www.w3schools.com/python/python_datatypes.asp)**.\n",
        "\n",
        "\n",
        "\n",
        "> ***A Variable is like a box in the computer’s memory where you can store a single value. — Al Sweigart***\n",
        "\n",
        "\n",
        "Unlike in other programming languages, in Python, you need not declare any variables or initialize them. Please read [this](https://stackoverflow.com/a/11008311/11646278).\n",
        "\n",
        "\n",
        "### **Syntax**\n",
        "\n",
        "\n",
        "The general syntax to create a variable in Python is as shown below:\n",
        "\n",
        "`variable_name = value`\n",
        "\n",
        "The `variable_name` in Python can be short as sweet as `a, b, x, y, ...` or can be very informative such as `age, height, name, student_name, covid, ...`\n",
        "\n",
        "\n",
        "> ***Although it is recommended keeping a very descriptive variable name to improve the readability.***\n",
        "\n",
        "\n",
        "\n",
        "### **Rules**\n",
        "\n",
        "**All set and done, there are some rules that you need to follow while naming a variable:**\n",
        "\n",
        "* A variable name must start with a ***letter*** or the ***underscore character***\n",
        "\n",
        "* A variable name cannot start with a ***number***\n",
        "\n",
        "* A variable name can only contain ***alpha-numeric characters*** and ***underscores***. For example, anything like this is valid: ***A-z, 0–9, and _***\n",
        "\n",
        "* Variable names are ***case-sensitive*** ***(height, Height***, and ***HEIGHT*** are three different variables names)\n",
        "\n",
        "### **Example**\n",
        "\n",
        "Below given is an example to properly initialize a value to a variable:"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "id": "NQKdREzkdw76",
        "colab_type": "code",
        "colab": {
          "base_uri": "https://localhost:8080/",
          "height": 35
        },
        "outputId": "70b43a3d-c3b4-4846-f786-64b07890bb4d"
      },
      "source": [
        "# This is a valid and good way to assign a value to a variable\n",
        "# For example you might want to assign values to variables to calculate the area of a circle\n",
        "\n",
        "pi = 3.142                                   # I could have also used \"math\" library (math.pi)\n",
        "radius = 5                                   # Interger value for radius\n",
        "area_of_circle = 0                           # Used to store the value of area of circle\n",
        "\n",
        "area_of_circle = pi * (radius) ** 2          # Area = (PI * R^2)\n",
        "\n",
        "print(\"The area of the circle based on the given data is: \", area_of_circle)"
      ],
      "execution_count": 1,
      "outputs": [
        {
          "output_type": "stream",
          "text": [
            "The area of the circle based on the given data is:  78.55\n"
          ],
          "name": "stdout"
        }
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {
        "id": "DIyEuUw8d3aU",
        "colab_type": "text"
      },
      "source": [
        "### **Pictorial Example (Skim it quickly)**\n",
        "I#  believe just by seeing a picture or an image, the concepts can be understood more quickly. Below is the pictorial representation of a variable and it being stored in the memory.\n",
        "\n",
        "\n",
        "![alt text](https://miro.medium.com/max/1050/1*dvv6ffYSxqTtd9wTB3TeKw.png)\n",
        "\n",
        "\n",
        "\n",
        "![alt text](https://miro.medium.com/max/1050/1*TQPtYle_1fHLVXvbpJICBA.png)\n",
        "\n",
        "\n",
        "---"
      ]
    }
  ]
}