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Message: <blockquote data-quote="gayan kalhara" data-source="post: 3307483" data-attributes="member: 60168">Hello, World2.1 What you should know You should know how to edit programs in a text editor or IDLE, save them to disk (floppy or hard) and run them oncethey have been saved. 2.2 Printing Programming tutorials since the beginning of time have started with a little program called Hello,World! So here it is:print "Hello, World!"If you are using the command line to run programs then type it in with a text editor, save it as ‘hello.py’ and run it with“python hello.py”Otherwise go into IDLE, create a new window, and create the program as in section 1.4.When this program is run here’s what it prints:Hello, World!Now I’m not going to tell you this every time, but when I show you a program I recommend that you type it in and runit. I learn better when I type it in and you probably do too.Now here is a more complicated program:print "Jack and Jill went up a hill"print "to fetch a pail of water;"print "Jack fell down, and broke his crown,"print "and Jill came tumbling after."When you run this program it prints out:Jack and Jill went up a hillto fetch a pail of water;Jack fell down, and broke his crown,and Jill came tumbling after.When the computer runs this program it first sees the line:print "Jack and Jill went up a hill"so the computer prints:Jack and Jill went up a hillThen the computer goes down to the next line and sees:print "to fetch a pail of water;"So the computer prints to the screen:to fetch a pail of water;The computer keeps looking at each line, follows the command and then goes on to the next line. The computer keepsrunning commands until it reaches the end of the program. 2.3 Expressions Here is another program:print "2 + 2 is", 2+2print "3 * 4 is", 3 * 4print 100 - 1, " = 100 - 1"print "(33 + 2) / 5 + 11.5 = ",(33 + 2) / 5 + 11.5And here is the output when the program is run:2 + 2 is 43 * 4 is 1299 = 100 - 1(33 + 2) / 5 + 11.5 = 18.5As you can see Python can turn your 50 thousand RS computer into a 150 RS  calculator.Python has six basic operations:Operation Symbol ExampleExponentiation ** 5 ** 2 == 25Multiplication * 2 * 3 == 6Division / 14 / 3 == 4Remainder % 14 % 3 == 2Addition + 1 + 2 == 3Subtraction - 4 - 3 == 1Notice that division follows the rule, if there are no decimals to start with, there will be no decimals to end with. (Note:This will be changing in Python 2.3) The following program shows this:4 Chapter 2. Hello, Worldprint "14 / 3 = ",14 / 3print "14 % 3 = ",14 % 3printprint "14.0 / 3.0 =",14.0 / 3.0print "14.0 % 3.0 =",14 % 3.0printprint "14.0 / 3 =",14.0 / 3print "14.0 % 3 =",14.0 % 3printprint "14 / 3.0 =",14 / 3.0print "14 % 3.0 =",14 % 3.0printWith the output:14 / 3 = 414 % 3 = 214.0 / 3.0 = 4.6666666666714.0 % 3.0 = 2.014.0 / 3 = 4.6666666666714.0 % 3 = 2.014 / 3.0 = 4.6666666666714 % 3.0 = 2.0Notice how Python gives different answers for some problems depending on whether or not there decimal values areused.The order of operations is the same as in math:1. parentheses ()2. exponents **3. multiplication *, division \, and remainder %4. addition + and subtraction - 2.4 Talking to humans (and other intelligent beings) Often in programming you are doing something complicated and may not in the future remember what you did.When this happens the program should probably be commented. A comment is a note to you and other programmersexplaining what is happening. For example:#Not quite PI, but an incredible simulationprint 22.0/7.0Notice that the comment starts with a #. Comments are used to communicate with others who read the program andyour future self to make clear what is complicated.</blockquote>

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