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python

(and large) free handbooks by G. van Rossum (the Python creator) are available on the net (try: http://www.python.org/doc/ for browsing or ftp://ftp.python.org for downloading).

How do I write a simple Python program?

Edit a text file that will contain your Python program. I can use the kde "kate" editor to do it (under X):
kate try_python.py &

Type in some simple python code to see if it works:

#!/usr/bin/env python
print 2+2

The first line (starting with the "pound-bang") tells the shell how to execute this text file--it must be there (always as the first line) for Linux to know that this particular text file is a Python script. The second line is a simple Python expression.

After saving the file, I make it executable:
chmod a+x try_python.py

after which I can run it by typing:
./try_python.py

Python is an excellent, and very modern programming language. Give it a try,  particularly if you like object oriented programming. There are numerous libaries/extensions available on the Internet. For example, scientific python (http://starship.python.net/crew/hinsen/scientific.html) and numeric python (http://sourceforge.net/projects/numpy) are popular libraries used in engineering.

Here is a slightly longer, but still (hopefully) self-explanatory python code. A quick note:  python flow control depends on the code indentation--it makes it very natural looking and forcing legibility, but takes an hour to get used to.

#!/usr/bin/env python
# All comments start with a the character "#"
# This program converts human years to dog years

# get the original age
age = input("Enter your age (in human years): ")
print           # print a blank line

# check if the age is valid using a simple if statement
if age < 0:
        print "A negative age is not possible."
elif age < 3 or age > 110:
        print "Frankly, I don't believe you."
else:
        print "That's the same as a", age/7, "year old dog."

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