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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.
Backquote, backtic, str and repr in Python - conversion object to string

The backquote or backtic operator in Python is a pseudonym for the repr function.

If you have an object that you want to convert into a string (to manipulate it, store it, print it out), Python may call one of two standard method:

__str__ (also the str function) converts an object into a human-readable form - the sort of thing that your program's user might wish to see if you print an object out.

__repr__ (also the repr function) converts an object into a string which is what you as the programmer would wish to be fed back for debugging purposes.

The base object class from which every objects is derived these days includes a __repr__ method which returns a string containing the object type and id / memory address. There is no __str__ method in the base object, and the system will fallback to running __repr__ if you try to print out / convert to a string an object for which __str__ has not been overwritten.

The Backquote (back quote, backtic, back tic) operator runs repr (hard to find in an online search, as the backquote if often special syntax to or ignored by search engines!)

Sample program and output - [here].
(written 2012-07-05, updated 2012-07-14)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
Y112 - Python - Objects - Intermediate
  [296] Using a Python dictionary as a holder of object attributes - (2005-04-30)
  [383] Overloading of operators on standard objects in Python - (2005-07-19)
  [477] Class, static and unbound variables - (2005-10-25)
  [656] Think about your design even if you don't use full UML - (2006-03-24)
  [831] Comparison of Object Oriented Philosophy - Python, Java, C++, Perl - (2006-08-13)
  [903] Pieces of Python - (2006-10-23)
  [964] Practical polymorphism in action - (2006-12-04)
  [1146] __new__ v __init__ - python constructor alternatives? - (2007-04-14)
  [1217] What are factory and singleton classes? - (2007-06-04)
  [1517] Python - formatting objects - (2008-01-24)
  [1644] Using a utility method to construct objects of different types - Python - (2008-05-17)
  [1661] Equality, sameness and identity - Python - (2008-05-31)
  [1819] Calling base class constructors - (2008-10-03)
  [2368] Python - fresh examples of all the fundamentals - (2009-08-20)
  [2409] TypeError: super() argument 1 must be type, not classobj (Python) - (2009-09-18)
  [2485] How do I set up a constant in Python? - (2009-10-31)
  [2693] Methods that run on classes (static methods) in Python - (2010-03-25)
  [2717] The Multiple Inheritance Conundrum, interfaces and mixins - (2010-04-11)
  [2720] Multiple inheritance in Python - complete working example - (2010-04-14)
  [2722] Mixins example in Python - (2010-04-14)
  [2764] Python decorators - your own, staticmethod and classmethod - (2010-05-14)
  [2785] The Light bulb moment when people see how Object Orientation works in real use - (2010-05-28)
  [2889] Should Python classes each be in their own file? - (2010-07-27)
  [2905] Defining static methods in Python - (2010-08-05)
  [2994] Python - some common questions answered in code examples - (2010-10-10)
  [3002] A list of special method and attribute names in Python - (2010-10-17)
  [3442] A demonstration of how many Python facilities work together - (2011-09-16)
  [3472] Static variables in functions - and better ways using objects - (2011-10-10)
  [3524] Metaclasses (Python) and Metatables (Lua) - (2011-11-17)
  [3887] Inheritance, Composition and Associated objects - when to use which - Python example - (2012-10-10)
  [4028] Really Simple Class and Inheritance example in Python - (2013-03-04)
  [4094] Python Properties - how and why - (2013-05-18)
  [4344] Python base and inherited classes, test harness and unit testing - new examples - (2014-12-07)
  [4356] Object factories in C++, Python, PHP and Perl - (2014-12-19)
  [4366] Changing what operators do on objects - a comparison across different programming languages - (2014-12-26)
  [4410] A good example of recursion - a real use in Python - (2015-02-01)
  [4449] Spike solution, refactoring into encapsulated object methods - good design practise - (2015-03-05)
  [4450] Deciding whether to use parameters, conditional statements or subclasses - (2015-03-05)
  [4541] Setting up and tearing down with the Python with keyword - (2015-10-16)
  [4649] Object and Static methods - what is the difference; example in Python 3 - (2016-02-17)
  [4717] with in Python - examples of use, and of defining your own context - (2016-11-02)
  [4718] Defining an object that is a modified standard type in Python - (2016-11-02)
  [4719] Nesting decorators - (2016-11-02)

Y108 - Python - String Handling
  [324] The backtick operator in Python and Perl - (2005-05-25)
  [463] Splitting the difference - (2005-10-13)
  [496] Python printf - (2005-11-15)
  [560] The fencepost problem - (2006-01-10)
  [773] Breaking bread - (2006-06-22)
  [943] Matching within multiline strings, and ignoring case in regular expressions - (2006-11-25)
  [954] Splitting Pythons in Bradford - (2006-11-29)
  [970] String duplication - x in Perl, * in Python and Ruby - (2006-12-07)
  [1110] Python - two different splits - (2007-03-15)
  [1195] Regular Express Primer - (2007-05-20)
  [1608] Underlining in Perl and Python - the x and * operator in use - (2008-04-12)
  [1876] Python Regular Expressions - (2008-11-08)
  [2284] Strings as collections in Python - (2009-07-12)
  [2406] Pound Sign in Python Program - (2009-09-15)
  [2692] Flexible search and replace in Python - (2010-03-25)
  [2721] Regular Expressions in Python - (2010-04-14)
  [2765] Running operating system commands from your Python program - (2010-05-14)
  [2780] Formatted Printing in Python - (2010-05-25)
  [2814] Python - splitting and joining strings - (2010-06-16)
  [3090] Matching to a string - what if it matches in many possible ways? - (2010-12-17)
  [3218] Matching a license plate or product code - Regular Expressions - (2011-03-28)
  [3349] Formatting output in Python through str.format - (2011-07-07)
  [3468] Python string formatting - the move from % to str.format - (2011-10-08)
  [3469] Teaching dilemma - old tricks and techniques, or recent enhancements? - (2011-10-08)
  [3886] Formatting output - why we need to, and first Python example - (2012-10-09)
  [4027] Collections in Python - list tuple dict and string. - (2013-03-04)
  [4152] Why are bus fares so high? - (2013-08-18)
  [4213] Formatting options in Python - (2013-11-16)
  [4307] Identifying and clearing denial of service attacks on your Apache server - (2014-09-27)
  [4360] Python - comparison of old and new string formatters - (2014-12-22)
  [4593] Command line parameter handling in Python via the argparse module - (2015-12-08)
  [4595] Python formatting update - including named completions - (2015-12-10)
  [4659] Prining a pound sign from Python AND running from the command line at the same time - (2016-03-03)


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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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