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For 2021 - online Python 3 training - see ((here)).

Our plans were to retire in summer 2020 and see the world, but Coronavirus has lead us into a lot of lockdown programming in Python 3 and PHP 7.
We can now offer tailored online training - small groups, real tutors - works really well for groups of 4 to 14 delegates. Anywhere in the world; course language English.

Please ask about private 'maintenance' training for Python 2, Tcl, Perl, PHP, Lua, etc.
this or self - what are they, and what is the difference? (Python)

In any object oriented language, you'll have a number of different objects of the same type, and you'll need to be able to refer to a paricular attribute within a particular object - usually, you'll call a named piece of code (a method) on an object and need to say "on THIS object" ... let me rephrase that in an example ...

I have two tables in my restaurant. One is made of glass and the other is made of pine. And I run a piece of code asking what material is THIS table made of. Depending on which table object I run my method on, the answer could be "this table is made of glass" or "this table is made of pine".

In Python, the first parameter to a normal (or dynamic or object) method in a class is the reference to the current object. In many of my demonstrations to newcomers, you'll find me using the name current for the variable, but it's most common to use self. And there's no reason at all why you can't use the variable name this. None of these are reserved words, and you can even vary the word you use from one method to the next. Code-wise, it's no more that a place holder; some tools may prefer you to use one word or another, though.

Example code - [here] - which used self, this and current, and a data file that goes with the example is [here]. The example also shows the use of a factory pattern (again, factory is just a name and we have actually called our method make)

Note - in some languages such as Java and PHP, the "current object" word is a reserved name rather than being declared at the top of the method, and you can't choose to change it from this.
(written 2012-12-08, updated 2012-12-15)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
Y106 - Object Oriented Python
  [477] Class, static and unbound variables - (2005-10-25)
  [834] Python makes University Challenge - (2006-08-15)
  [900] Python - function v method - (2006-10-20)
  [1306] Python class rattling around - (2007-08-16)
  [1348] Screw it or Glue it? Access to Object variables - a warning - (2007-09-12)
  [1925] Introduction to Object Oriented Programming - (2008-12-06)
  [2017] Python - a truly dynamic language - (2009-01-30)
  [2169] When should I use OO techniques? - (2009-05-11)
  [2604] Tips for writing a test program (Ruby / Python / Java) - (2010-01-29)
  [3085] Object Oriented Programming for Structured Programmers - conversion training - (2010-12-14)
  [3399] From fish, loaves and apples to money, plastic cards and BACS (Perl references explained) - (2011-08-20)
  [3436] Moving from scripting to Object Orientation in Python - (2011-09-13)
  [3673] Object oriented or structured - a comparison in Python. Also writing clean regular expressions - (2012-03-26)
  [3878] From Structured to Object Oriented Programming. - (2012-10-02)
  [4021] Spike solution, refactored and reusable, Python - Example - (2013-02-28)
  [4028] Really Simple Class and Inheritance example in Python - (2013-03-04)
  [4129] Simple OO demonstration in C++, comparison to Python - (2013-07-01)
  [4448] What is the difference between a function and a method? - (2015-03-04)
  [4591] From single block to structure and object oriented programming - (2015-12-02)
  [4650] Why populate object with values as you construct them? - (2016-02-18)
  [4721] When to check an object type - Python isinstance example - (2016-11-03)


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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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