Python Database Connectivity for beginners

Hi guys,

I am back again to blog, dint got much of a time to really get going these days that was why the break. Any ways back to the topic and this time its Python. I am going to explain here just the basic thing u need to do for a database connectivity with some database like SQLite or Access or SQLyog..or whatever...the point is u would be able to access your data through ur program/script

This can be little tricky b'coz of a few reasons, Firstly b'coz that python does not have any kind of variable declaration and opening and closing braces which the normal c/c++ or other high end programmers find annoying..(well.. atleast i did).

Secondly b'coz if u are using sqlite and python then it uses transactions by default..

dint get it??? well lemme explain..

Before every INSERT/UPDATE/DELETE/REPLACE statement, Python’s sqlite3 implicitly opens a transaction. It automatically commits before a non-query statement, e.g. before a CREATE TABLE statement or similar. This is kind of cool thing b'cos if an exception is thrown while you’re inserting data, the state of the database is not affected...BUT..

when u open a db insert some values and close it...and then open it again and give a select query...u will get nothing and u can see the table is blank...

i played around a lot with this and finally i got to know about the python transaction thing...the solution is simple just commit the changes after each transaction.

so now..lets get our hands dirty with some python code

so the very first line..
python code starts with the very first line refering to the intrepreter of python nad would look like
#! c:/Python25/Python -for windows
#! user/bin/python-for linux

dbFile = "path of the db file"

#if your are using for a cgi file youmay need to import cgi library

import sqlite3

db = sqlite3.connect(dbFile)

c = db.cursor()

#creating table

c.execute('''create table stocks (date text, trans text, symbol text, qty real, price real)''')

#inserting a row of data
c.execute("""insert into stocks values ('2009-02-15','DPK','COOL',247,00.15)""")

#save (commit) the changes
db.commit()

c.close();

Yep..!!! Thats IT....the database is done and to view the datas you entered you can use the following code

>>>c = db.cursor()
>>>c.execute('select * from stocks')
>>>for row in c:
print row

( u'2009-02-15', u'DPK', u'COOL',247,00.15)

Well....thats all Folks!...see ya all in my next blog..Have fun!

ScreenBoard in AIR

Guys, this is an extension of whiteboard application. there is not much of a difference here in both the thing is here the application is transparent and gives the user a feeling that the application is drawing actually on the screen. Alright so lets see how the thing is being done..I assume the reader have some basic idea about flex/AIR. if not its not a big deal..

Actual code is very simple and hence i am not going to let it get complicated, because every one likes it simple right?

Firstly u can begin with a new AIR project
type the script tag and inside that type the following code.

import mx.core.UIComponent;
import flash.display.*;

private var spBoard:Sprite = new Sprite();

private function init():void
{
var win:NativeWindow = systemManager.stage.nativeWindow;
var cont:UIComponent = new UIComponent();
win.maximize();
win.visible = true;
}

/*In this function the mouse position is taken and the graphics function starts drawing
you can set the line style from 3 to any number u like or u can get it from a UI text
box or anything u like , u can use a colour picker to set the color of the line but i am
using a simple black line with 3 brush points.
*/
private function onMouseDown():void
{
dboard.graphics.lineStyle(3, 0x000000);
dboard.graphics.moveTo(stage.mouseX, stage.mouseY);
}

/*
Here the lines end point is calculated from the x,y of mouse. What this actually doies is draws tiny straight lines to each place u move your mouse
*/
private function onMouseMove(e:MouseEvent):void
{
if (!e.buttonDown)
{
return;
}
dboard.graphics.lineTo(stage.mouseX, stage.mouseY);
e.updateAfterEvent();
}

important to note:

*board is the canvas id and set its attributes as alpha=.08,
*call the onmousedown function on the mouse down event in the canvas (i.e board) and onmousemove on the mousemove event of canvas

* dboard is another canvas over which u are actually drawing set its height and width to 100%
* u cn add a button and on its click event type {dboard.graphics.clear()} to clear the screen.
And DONT FORGET TO SET THE showFlexChrome="false" in your windowedApplication tag
If that even doesnt work under any circumstances u may edit the xml file and set the transparency to true and also the showChrome tag to false Which is inside the "initialWindow" tag
thats it..have a nice time sracthing ur desktop...