Writing Simple programs in Python(cont.)

To start writing simple programs in Python, we have to know firstly the SW development process and then we also have to know a bit about the language in which we wish to code,in this case,python, to get started. Since all programs take some kind of input,process it and then produce the results,if we know just how to get data from the user,process it and produce output in a readable form, we would be well on the road to learning how to code. We begin by looking at the notion of a variable.

                                                              What is a variable?

Simply stated,a variable is name assigned to a value. For example, 

                                                               n = 5

here, n is a variable given the value 5.Whenever n appears in an expression, its value,5 will be substituted. Now,let us take a look at some basic mathematical operators in Python.

                                                         Some basic Arithmetic Operators.

                                             + = Addition

                                              - = Subtraction

                                             * = Multiplication

                                             / = Division

                                            ** = Exponentiation.

Now,we will look at basic I/O.

                                                       Basic I/O

In order to get information from the user, Python uses the input statement,as shown below

                                               name = input("Enter your name:")

This statement,when executed by the Python interpreter,display the string within quotes,prompting the user to enter his name,as shown below:

                                         Enter your name:Rajesh

Here,Rajesh is our response.

Now, to display information to the user, we use the function print. It may be used just to display a message or output the value of a variable or a result of some processing or to display a combination of some strings and variables.

Thus, in Python, input is used to get information from the user and print is used to display information on the screen.

In my earlier lesson, we saw a program in Python which calculates the future value of an investment. Those of you who could not fully understand the program then now will be able to,in light of the elements discussed here(I/O statements,operators etc),comprehend fully the program now. Let us take another example of a simple program in python which calculates the Fahrenheight equivalent of a given celsius temperature. Our program should take a celsius temperature from the user and then print the fahrenheight equivalent. Simple! The algorithm of the program is:

                                     Input the temperature in degrees Celsius (call it celsius)
                                     Calculate fahrenheit as 9/5 celsius + 32
                                     Output fahrenheit.

And the full program in Python:

                     Note:Take input from the user.

                     cel = input("What is the Celsius Temperature")

                     x = 9/5
                     y = x * int(cel)

                     fint = y + 32

                     Note: I have broken the formula of calculating celsius temperature into fahrenheight into 

                             steps for easy calculation. int(cel) is used for converting the value into an int. I have 

                             used it my interpreter,Python 3.3.1 which was not interpreting it correctly without the 

                            int conversion.

                      Note : Display output.
                     print("Fahrenheight Temperature = "+str(fint))

 So,thus,I hope that users will now be able to start writing simple programs in Python on their own. Of course this is just the beginning! As they progress and learn more details of the language, they will be able to write more sophisticated programs in Python!

Note : Here and in my earlier lesson, I have assumed that students know how to start the IDLE of Python and write and run a program in it. Although the process is quite simple I intend, in the next lesson, to teach students how to create and run a Python Program using the Python IDLE,in case they dont know! Not only we must know the language reading from a book,we must also know how to write a program in it,run it and test it! And with that Students will be able to write simple programs easily enough!