♠ Posted by Unknown in Python
Reading Input from the Console in Python
The input() function
asks the user to input a value for the variable. Default value entered as a
string.
Python: Comments
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Comments in Python
In Python, comments are preceded by a pound sign (#) on
a line, called a line comment, or enclosed between three consecutive single
quotation marks (''') on one or several lines, called a paragraph comment. When
the Python interpreter sees #, it ignores all text after # on the same line.
When it sees ''', it scans for the next ''' and ignores any text between the
triple quotation marks.
For Example:
# This program displays one message
''' This program displays
Two messages
'''
Line Continuation Symbol in Python
In some cases, the Python
interpreter cannot determine the end of the statement written in multiple
lines. We can place the line
continuation character (\) at the end of the line to tell the interpreter
that the statement is continued on the next line. For example, the following
statement
fact = 1 * 2 * 3 * 4 *
\
5 * 6
is equivalent to
fact = 1 * 2 * 3 * 4 *
5 * 6
Python: Creating Source Code Files
♠ Posted by Unknown in Python
Creating Source Code File in Python
Entering Python Statement
at the statement prompt >>> is convenient, but the statements
are not saved. To save statements for later use, you can create a python file
to store the statements. The file can be created using editor, that file is
called a Python source file or script file, or module. By
convention, Python files are named with the extension .py.
Running a Python
program from a script file is known as running Python in script mode.
Typing a statement at the statement prompt >>> and executing it
is called Python in interactive mode.
To create new Python
file in IDLE, select file menu à New
File. It opens new file window type following lines and save it as “Example01.py”.
Now Click Run (F5) from Run menu of window. Control transfer to IDLE statement
prompt and show the output.
Example:
Example01.py
#Display two messages
print(“Welcome to
world of Python…”)
print(“Hello Friends…”)
Python: Getting Started
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Getting Started with Python
Let’s get started by writing
a simple Python program that displays the message “Welcome to world of
Python…” on the console.
Assume you have Python
installed on the OS. You can start Python in a command window by typing “Python”
at the command prompt, as shown in below figure. Or by using IDLE,
as shown in another figure. IDLE (Interactive DeveLopment Environment)is an
Integrated Development Environment (IDE) for Python.
Python command-line
and IDLE can also be accessed directly from the Windows Start menu and
in Python group.
Python: History
♠ Posted by Unknown in Python
Python: History
Since 1990, Python was
created by Guido van Rossum in the Netherland and was named after well-known British
Monty Python’s Flying Circus. Rossum developed Python as a hobby, and Python
has become a popular programming language widely used in industry and academia
due to its simple, concise, and intuitive syntax and extensive library.
Python is a
general-purpose programming language. That means you can use Python to
write code for any programming task. Python is now used in the Google Search
Engine, in mission-critical projects at NASA, and in transaction processing at
the New York Stock Exchange.
Python is interpreted,
which means that Python code is translated and executed by an interpreter.
Python is an object-oriented programming (OOP)
language. Data in Python are objects created from classes.
Adv Java - [Java Server Page: Session Management]
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Java Server Page Session Management
The HTTP is stateless protocol. The state management is a necessary management technique to preserve current page data from moving one page to another page. The Session management is one type of state management to maintain particular user login/logout session tracking. The Session is created individually for every particular user who are getting logged in/out on website.
Adv Java - [Java Server Pages: Scripting Elements]
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JSP Scripting Elements
Once the directives have been used to
setup the scripting environment you can utilize the scripting language
elements. JSP1.1. has three scripting language elements – declaration,
scriptlets, and expressions. A declaration will declare elements, a scriptlet
is a statement fragment, and an expression is a complete language expression.
In JSP each scripting element begins with a “<%”.
Adv Java - [Servlet: Hidden Field]
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Hidden Field in Servlet Example
The HTTP is stateless protocol, means it can not preserve data of current web page while moving backward/forward web pages. The hidden field is a way to State management in servlet example. The hidden field is used to store intermediate data hide while moving from one page to another page.
Adv Java - [Servlet: Useful Methods]
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Useful Methods of Servlet
Servlets are simply Java classes that follow
three basic rules:
- An
HTTP Servlet must extend javax.servlet.http.HttpServlet (or extend an
abstract class that does).
- The
Servlet must implement at least one of the following metheods: doGet(),
doPost(), doPut(), doDelete(), init(), destroy(), or service().
- The Servlet can optionally implement init(), destroy(), or getServletInfo().
Adv Java - [Servlet: Multithreaded]
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Multithreading into Servlet
The servlet container has a pool of
threads that it will dispatch to handle client requests. It is quite likely
that two clients arriving at the same time could be processing through your
service() at the same time. Therefore the service() method must written in a
thread-safe manner. Any access to common resources will need to be guarded by
using the synchronized keyword.
Adv Java[Servlet: Session Management]
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Servlet Session Management
HTTP is a “sessionless” protorcol, so you
cannot tell from one server hit to another if you’ve got the same person
repeatedly querying your site. Or if it is a completely different person. A
great deal of effort has gone into mechanisms that will allow Web developers to
track sessions. Companies could not do e-commerce without keeping track of a
client and the items they have put into their shopping cart, for example.
Adv Java [Servlet: Life Cycle]
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Servlets
Client access from the Internet or
corporate intranets is a sure way to allow many users to access data and
resources easily. This type of access is based on clients using the World Wide
Web standards of Hypertext Markup Language (HTML) and Hyper Text Transfer
Protocol (HTTP). The Servlet API set abstracts a common solution framework for
responding to HTTP requests.
Adv Java - [JDBC: Resultset Types]
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JDBC Resultsets
Before JDBC 2.1, a ResultSet object created by
executing a statement was, by default, forward-only scrollable. That is, we
could traversse through the resultset using the next() method only. next()
returns false when the last record is reached, and no more details can then be
retrieved.
Adv Java - [JDBC: Prepared Statement]
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JDBC Prepared Statement
JDBC prepared statements address the following
requirements:
- Creating parametrerized statements such that data for parameters can be substituted dynamically.
- Creating statements involving data values that cannot always be represented as character strings.
- Pre-compiling SQL statements to avoid repeated compiling of the same SQL statements.
Adv Java - [JDBC: SQL Classes]
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JDBC SQL Classes
The JDBC classes and interfaces remain in two Java
packages : java.sql and javax.sql:
- java.sql :- This package contains classes and interfaces designed with traditional client-server architecture in mind. Its functionality is focused primarily on basic database programming services such as creating connections, executing statements and prepared statements, and running batch queries. Advanced functions such as batch updates, scrollable resultsets, transaction isolation, and SQL data types are also available.
Adv Java - [JDBC: Introduction]
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JDBC [Java DataBase Connectivity]
Introduction:
It has been estimated that half of all software
development involves client/server operations. A great promise of Java has been
the ability to build platform-independent client/server database applications.
This has come to fruition with Java DataBase Conectivity (JDBC).
Adv Java [JAR File Creation]
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What is JAR files?
A JAR file allows
you to efficiently deploy a set of classes and their associated resource. For example, a developer may build a
multimedia application that uses various sound and image files. A set of Beans
can control how and when this information is presented. All these pieces can be
placed into one JAR files.
Adv Java - [Swing: File Dialogs]
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File Dialogs
Some
operating systems have a number of special built-in dialog boxes to handle the
selection of things such as fonts, colors, printer, and the like. Virtually all
graphical operating systems support the opening and saving of files, however
and so Java’s JFileChooser encapsulates these for easy use.
Adv Java - [Swing: Menu]
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Java Swing Menus
Adv Java - [Swing: JOptionPane Class]
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JOptionPane Class
Windowing
environments commonly contain a standard set of message boxes that allow you to
quickly post information to the used or to capture information form the user.
In Swing, these message boxes are contained in JOptionPane. You have many
different possibilities, but the ones you’ll most commonly use are probably the
message dialog and confirmation dialog, invoked using the static
JOptionPane.showMessageDialog() and JOptionPane.showConfirmDialog().
Adv Java - [Swing: JList Class]
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JList Class
List
boxes are significantly different from JComboBox boxes, and not just in
appearance. While a JcomboBox box drops down when you activate it, a JList
occupies some fixed number of lines on a screen all the time and doesn’t
change. If you want to see the items in a list, you simply call
getSelectedValues(), which produces an array of String of the items that have
been selected.
Adv Java - [Swing: JScrollPane Class]
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JScrollPane Class
A
scroll panes is a component that presents a rectangular area in which a
component may be viewed. Horizontal and/or vertical scroll bars may be provided
if necessary. Scroll panes are implemented in Swing by the JScrollPane class,
which extends JComponent.
Adv Java - [Swing: JTabbedPane Class]
♠ Posted by Unknown in Adv Java
JTabbedPane Class
A tabbed panes is a component that appears
as a group of folders in a file cabinet. Each folder has a title. When a user
selects a folder, its contents become visible. Only one of the folders may be
selected at a time. Tabbed panes are commonly used for setting configuration
options.
Adv Java - [Swing: JComboBox Class]
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JComboBox Class
Swing
provides a combo box (a combination of a text field and a drop-down list)
through the JComboBox class, which extends JComponent. A combo box normally displays
one entry. However, it can also display a drop-down list that allows a user to
select a different entry. You can also type your selection into the text field.
