Python-1(Introduction,Variables,Statements)

1.Introduction To Python:

1.1 What is Python:

Python is a popular high level programming language. It was created in 1991 by Guidovan Rossum.

       It is used for:

  • web development (server-side),
  • software development,
  • mathematics,
  • system scripting.

1.2 Application of the python:

  • Python can be used on a server to create web applications.
  • Python can be used alongside software to create workflows.
  • Python can connect to database systems. It can also read and modify files.
  • Python can be used to handle big data and perform complex mathematics.
  • Python works on different platforms (Windows, Mac, Linux, Raspberry Pi, etc).
  • Python has syntax that allows developers to write programs with fewer lines than some other programming languages.
  • Python runs on an interpreter system, meaning that code can be executed as soon as it is written. This means that prototyping can be very quick.
  • Python can be treated in a procedural way, an object-orientated way or a functional way.

2. Variables in Python:

2.1 Defining a variable:

      One of the most powerful features of the programming language is ability to manipulate variable. A variable is a name that refer to a value. Python is dynamically typed, which means that you don't have to declare what type each variable is. An assignment  statement create new and gives them values

      Examples:                

               message = ’python example program’

                n = 17

                pi = 3.1415798794

      This example makes three assignments. The first assigns a string to new variable named  message , the second assigns the integer 17 to n, the third assigns the (approximate) value of pi to variable pi.

2.2 Rules for defining variable:

  • A variable name must start with a letter or the underscore character
  • A variable name cannot start with a number
  • A variable name can only contain alphanumeric characters and underscores (A-z, 0-9, and _ )
  • Variable names are case-sensitive (age, Age and AGE are three different variable)

2.3 Displaying the variable

      To display the value of the variable we use the print statement

       Example             

               >>Print(n)

               17

               >>print(pi)

               3.1415798794
  • Type of the variable is the type of the value it refers to. 

3. Statements:

     A statement is a unit of code that the python interpreter can execute. We have seen two kinds of  statement they are

  1. Print being an expression statement
  2. Assignment statement

    When you type a statement in interactive mode ,the interpreter execute it and display the result, if there is one. A script usually contains sequence of statement, if there is more than one statement, the result appear one at the a time as the statement execute.

    Example:              

               >>Print(1)

               >>x=2

               >>print(x)

     Output:

               1

               2

     Conclusion: The assignment operator produce no output.

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