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Python 2 Tutorial

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Python

In Greek mythology, Python is the name of a a huge serpent and sometimes a dragon. Python had been killed by the god Apollo at Delphi. Python was created out of the slime and mud left after the great flood. He was appointed by Gaia (Mother Earth) to guard the oracle of Delphi, known as Pytho.
The programming language Python has not been created out of slime and mud but out of the programming language ABC. It has been devised by a Dutch programmer, named Guido van Rossum, in Amsterdam.

Origins of Python

Guido van Rossum wrote the following about the origins of Python in a foreword for the book "Programming Python" by Mark Lutz in 1996:
"Over six years ago, in December 1989, I was looking for a "hobby" programming project that would keep me occupied during the week around Christmas. My office (a government-run research lab in Amsterdam) would be closed, but I had a home computer, and not much else on my hands. I decided to write an interpreter for the new scripting language I had been thinking about lately: a descendant of ABC that would appeal to Unix/C hackers. I chose Python as a working title for the project, being in a slightly irreverent mood (and a big fan of Monty Python's Flying Circus)."

 

Warnung:

Python2 is not supported anymore and shouldn't be used! Please consult our Python3 tutorial:

This chapter for Python3:

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German Version / Deutsche Übersetzung

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Classroom Training Courses

This website contains a free and extensive online tutorial by Bernd Klein, using material from his classroom Python training courses.

If you are interested in an instructor-led classroom training course, you may have a look at the Python classes
by Bernd Klein at Bodenseo. © kabliczech - Fotolia.com

Quote of the Day:

"Language designers want to design the perfect language. They want to be able to say, "My language is perfect. It can do everything." But it's just plain impossible to design a perfect language, because there are two ways to look at a language. One way is by looking at what can be done with that language. The other is by looking at how we feel using that language - how we feel while programming." (-Yukihiro 'Matz' Matsumoto)

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If you have the choice working with Python 2 or Python 3, we recomend to switch to Python 3! You can read our Python Tutorial to see what the differences are.

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Lists

Changing Lists

This chapter of our tutorial deals with further aspects of lists. You will learn how to append and insert objects to lists and you will also learn how to delete and remove elements by using 'remove' and 'pop'

A list can be seen as a stack. A stack in computer science is a data structure, which has at least two operations: one which can be used to put or push data on the stack and another one to take away the most upper element of the stack. The way of working can be imagined with a stack of plates. If you need a plate you will usually take the most upper one. The used plates will be put back on the top of the stack after cleaning. If a programming language supports a stack like data structure, it will also supply at least two operations:

• push
  This method is used to put a new object on the stack. Depending on the point of view, we say that we "push" the object on top or attach it to the right side. Python doesn't offer - contrary to other programming languages - no method with the name "push", but the method "append" has the same functionality.
• pop
  This method returns the most upper element of the stack. The object will be removed from the stack as well.
• peek
  Some programming languages provide another method, which can be used to view what is on the top of the stack without removing this element. The Python list class doesn't possess such a method, because it is not needed. A peek can be simulated by accessing the element with the index -1:

  >>> lst = ["easy", "simple", "cheap", "free"]
  >>> lst[-1]
  'free'
  >>> 
  

How to continue: We are maintaining 4 different Python tutorials: A German and an English tutorial dealing with Python 2 and a tutorial on Python3 in English and German. This means an enormous amount of work. To reduce this work load, we decided to solely concentrate on the two Python3 tutorials. You can continue reading The Python3 Tutorial on Lists!