Non-Programmer's Tutorial for Python 2.6/Count to 10

While loops.
Here we present our first "control structure". Ordinarily, the computer starts with the first line and then goes down from there. However, control structures change the order of how the statements are executed and/or decide if a certain statement(s) will be run. Here's the source for a program that uses the codice_1 control structure:
a = 0
while a &lt; 10:
 a = a + 1
 print (a)
And here is the extremely exciting output: 
 1
 2
 3
 4
 5
 6
 7
 8
 9
 10
And you thought it couldn't get any worse after turning your computer into a five dollar calculator?
So what does the program do? First, it sees the line codice_2 which tells the computer to sets codice_3 to the value of zero. Then, it sees codice_4 which tells the computer to check whether codice_5. The first time the computer sees this while statement, codice_3 is equal to zero, which means codice_3 is less than 10, so the computer proceeds to run the succeeding indented, or tabbed in, statements. After the last statement, codice_8, within this while "loop" is run, the computer goes back up again to the codice_9 to check the current value of codice_3. In other words, as long as codice_3 is less than ten, the computer will run the tabbed in statements. With codice_12 repeatedly adding one to codice_3, eventually the while loop makes codice_3 equal to ten, and makes the codice_5 no longer true. Reaching that point, the program will not run the indented lines any longer.
Always remember to put a colon ":" after the "while" statement!
Here is another example of the use of codice_1:
a = 1
s = 0
print ('Enter Numbers to add to the sum.')
print ('Enter 0 to quit.')
while a != 0:
 print 'Current Sum:', s
 a = input('Number? ')
 s = s + a
print 'Total Sum =', round(s, 2)
 Enter Numbers to add to the sum.
 Enter 0 to quit.
 Current Sum: 0
 Number? 200
 Current Sum: 200
 Number? -15.25
 Current Sum: 184.75
 Number? -151.85
 Current Sum: 32.9
 Number? 10.00
 Current Sum: 42.9
 Number? 0
 Total Sum = 42.9
Notice how codice_17 is only run at the end. The codice_1 statement only affects the lines that are indented with whitespace. The codice_19 means "does not equal" so codice_20 means: "until codice_21 is zero, run the tabbed statements that follow." 
Infinite loops.
Now that we have while loops, it is possible to have programs that run forever. An easy way to do this is to write a program like this:
while 1 == 1:
 print "Help, I'm stuck in a loop."
The "==" operator is used to test equality of the expressions on the two sides of the operator, just as "&lt;" was used for "less than" before (you will get a complete list of all comparison operators in the next chapter).
This program will output codice_22 until the heat death of the universe or until you stop it, because 1 will forever be equal to 1. The way to stop it is to hit the Control (or "Ctrl") button and "C" (the letter) at the same time. This will kill the program. (Note: sometimes you will have to hit enter after the Control-C.)
Examples.
Fibonacci.py
a = 0
b = 1
count = 0
max_count = 20
while count &lt; max_count:
 count = count + 1
 # we need to keep track of a since we change it
 old_a = a
 old_b = b
 a = old_b
 b = old_a + old_b
 # Notice that the , at the end of a print statement keeps it
 # from switching to a new line
 print(old_a),
Output:
 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181
Note the output on a single line by use of a comma at the end of the codice_23 statement.
Password.py
password = "no password"
while password != "unicorn":
 password = raw_input("Password: ")
print "Welcome in"
Sample run:
 Password: auo
 Password: y22
 Password: password
 Password: open sesame
 Password: unicorn
 Welcome in
Exercises.
Write a program that asks the user for a Login Name and password. Then when they type "lock", they need to type in their name and password to unlock the program.