Developing in 60 MinutesLinux and PythonLinux and Python

Developing in 60 Minutes

Chapter Six: Tutorial

The material in this SlideShare is developed from the book:

“Developing in 60 Minutes: Linux and Python” by Jedidiah Reeser

JedidiahReeser.com/books

Also available on Amazon.com

Additional Media

Sample files and a demo video are available at:

JedidiahReeser.com/books

To begin, open your text editor and type in the sample file below and save as “dev_in_60_sample.txt”.

Now open up a new file and save it as“dev_in_60.py”

In your editor, add the following line of code, as the first line of the “dev_in_60.py”. The first line is the shebang line and will indicate that the script should use the Python interpreter for processing the commands in the file.

#!/usr/bin/env python

Now add the code below to open the file so you can access its contents. In order to open a file, you can use the “open” method. We pass in the name of the file, "dev_in_60_sample.txt”, and that we want to append, “a”, to the file. If you use the “with” command, it will help ensure that your file safely closes and frees up system resources.

with open(‘dev_in_60_sample.txt’, 'a') as f:

Next, add the text “Hello World!” to the end of the “dev_in_60_sample.txt” file by indenting with four spaces and typing the following line:

Notice how the string ends with “\n”? That will add a newline character.

f.write('Hello World!\n')

The script now opens the file and appends a line of text to the end. To confirm that the code was successfully implemented, you will need to open the file and print out the lines onto the screen.

To open the file with read only access, use the with open command used earlier and change the “a” to a “r”.

with open(‘dev_in_60_sample.txt’, 'r') as f:

To iterate over each line in the file and print it on the terminal, you can treat the file like a list. In Python, you can use a for loop to iterate over the file. It is as simple as:

for line in f: print line

To test the script, run the following command in the directory where you made the file:

python dev_in_60.py

Your screen output should look like the image below:

Congratulations! You have finished writing your first Python script in

the Linux environment.

jedidiahreeser.com/books