Page 50 - Information_Practice_Fliipbook_Class11
P. 50

Type the command 7+5 and press the Enter key. The interpreter executes the command by evaluating the expression
        7+5 and displaying the result. As shown in Fig 2.5, a short description of the error is displayed in case of an erroneous
        command. As Python interpreter provides feedback to the user interactively, we say that it is working in the interactive
        mode.

















                                             Fig 2.4 Executing a Python instruction

        While entering the next command, we forgot to write an operator between the operands 7 and 5. So, IDLE points out
        a syntax error (Fig 2.5).

















                                                Fig 2.5 IDLE's prompt to Exiting



               The Python Installer for Windows includes IDLE, by default.


        2.5.2 Python Editor

        To be able to save multiple instructions for future use in the form of a file (typically having a .py  extension), we
        use the Python Editor. To use the IDLE editor, follow the sequence of clicks: <File> <new>. A file containing Python
        instructions is called a Python script or a Python program, and working with Python scripts is called working in the
        script mode. To keep the Python script simple, we just type three instructions in the file:
          The first line is an instruction for printing a line of exclamation marks.
          The second line is an instruction to print a welcome message.

          The third line is again an instruction for printing a line of exclamation marks.
        Before  proceeding  further,  let  us  note  that  the  print()  instruction  is  used  to  display  the  output  produced
        on the execution of a Python script on the standard output i.e., the monitor. The text to be displayed is enclosed
        between the quotes (single quotes or double quotes). For example, in the first line, the text (also called a string)
        !!!!!!!!!!!!!!!!!!!!!!!!!!!!! is enclosed between the single quotes as '!!!!!!!!!!!!!!!!!!!!!!
        !!!!!!!'. This string could also be expressed as: "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!". However, in this book,
        we prefer to use single quotes. It is pertinent to mention that the numerical values and numerical expressions are not
        enclosed within quotes. We will learn more about print() in the upcoming chapters.

          36   Touchpad Informatics Practices-XI
   45   46   47   48   49   50   51   52   53   54   55