I'm not keen on recursive code - code that calls itself. Very often, such code is elegant in a way, yet so 'clever' that it is hard to follow. There are, however, exceptions where I say
"THAT is a good use of recursion". Once such is in the handling / parsing of RSS (Really Simple Syndication) feeds.
I was asked by one of my delegates about how he might download and analyse an RSS feed in Python ... and after a quick scout around, we downloaded
feedparser. The code to grab the feed is silly-trivial:
import feedparser
stuff = feedparser.parse("http://www.wellho.net/horse/index.xml")
stuff, though, is a dictionary that contains other dictionaries, lists, and strings ... and those other dictionaries and strings contain further dictionaries and strings and lists. After all, RSS is an XML feed and the parse method give you back something synonymous with a DOM object.
So I have "pretty print"ed
stuff using a function I wrote called
display_dict which itself calls
display_dict and
display_list as appropriate.
display_list itself calls
display_list and
display_dict. You can see the source at
[link] (written 2009-11-18, updated 2009-11-20)
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
Y151 - Python & XML [2378] Handling XML in Perl - introduction and early examples - (2009-08-27)
[2555] Bookkeeping - (2009-12-29)
[3082] XML handling in Python - SAX, DOM and XSLT examples - (2010-12-09)
[4594] XML handling in Python - a new teaching example using etree - (2015-12-09)
[4710] Searching a Json or XML structure for a specific key / value pair in Python - (2016-10-30)
Y117 - Python - Already written modules [2020] Learning Python - many new example programs - (2009-01-31)
[2890] Dates and times in Python - (2010-07-27)
[2931] Syncronise - software, trains, and buses. Please! - (2010-08-22)
[3442] A demonstration of how many Python facilities work together - (2011-09-16)
[3465] How can I do an FTP transfer in Python? - (2011-10-05)
[3479] Practical Extraction and Reporting - using Python and Extreme Programming - (2011-10-14)
[4085] JSON from Python - first principles, easy example - (2013-05-13)
[4086] Cacheing class for Python - using a local SQLite database as a key/value store - (2013-05-14)
[4441] Reading command line parameters in Python - (2015-02-23)
[4452] Binary data handling - Python and Perl - (2015-03-09)
[4696] Programming with random numbers - yet re-using the same values for testing - (2016-06-22)
[4697] Month, Day, Year number to day of week and month names in Python - English and Swedish - (2016-06-23)
[4708] Scons - a build system in Python - building hello world - (2016-10-29)
Y105 - Python - Functions, Modules and Packages [96] Variable Scope - (2004-10-22)
[105] Distance Learning - (2004-10-31)
[294] Python generator functions, lambdas, and iterators - (2005-04-28)
[303] Lambdas in Python - (2005-05-06)
[308] Call by name v call by value - (2005-05-11)
[340] Code and code maintainance efficiency - (2005-06-08)
[386] What is a callback? - (2005-07-22)
[418] Difference between import and from in Python - (2005-08-18)
[561] Python's Generator functions - (2006-01-11)
[668] Python - block insets help with documentation - (2006-04-04)
[745] Python modules. The distribution, The Cheese Shop and the Vaults of Parnassus. - (2006-06-05)
[749] Cottage industry or production line data handling methods - (2006-06-07)
[775] Do not duplicate your code - (2006-06-23)
[821] Dynamic functions and names - Python - (2006-08-03)
[900] Python - function v method - (2006-10-20)
[912] Recursion in Python - (2006-11-02)
[913] Python - A list of methods - (2006-11-03)
[949] Sludge off the mountain, and Python and PHP - (2006-11-27)
[959] It's the 1st, not the 1nd 1rd or 1th. - (2006-12-01)
[1134] Function / method parameters with * and ** in Python - (2007-04-04)
[1163] A better alternative to cutting and pasting code - (2007-04-26)
[1202] Returning multiple values from a function (Perl, PHP, Python) - (2007-05-24)
[1464] Python Script - easy examples of lots of basics - (2007-12-08)
[1784] Global - Tcl, PHP, Python - (2008-09-03)
[1790] Sharing variables with functions, but keeping them local too - Python - (2008-09-09)
[1869] Anonymous functions (lambdas) and map in Python - (2008-11-04)
[1870] What to do with a huge crop of apples - (2008-11-04)
[1871] Optional and named parameters in Python - (2008-11-05)
[1879] Dynamic code - Python - (2008-11-11)
[2011] Conversion of OSI grid references to Eastings and Northings - (2009-01-28)
[2439] Multiple returns from a function in Python - (2009-10-06)
[2440] Optional parameters to Python functions - (2009-10-07)
[2481] Sample code with errors in it on our web site - (2009-10-29)
[2520] Global and Enable - two misused words! - (2009-11-30)
[2718] Python - access to variables in the outer scope - (2010-04-12)
[2766] Optional and named parameters to Python functions/methods - (2010-05-15)
[2878] Program for reliability and efficiency - do not duplicate, but rather share and re-use - (2010-07-19)
[2929] Passing a variable number of parameters in to a function / method - (2010-08-20)
[2994] Python - some common questions answered in code examples - (2010-10-10)
[2998] Using an exception to initialise a static variable in a Python function / method - (2010-10-13)
[3159] Returning multiple values from a function call in various languages - a comparison - (2011-02-06)
[3280] Passing parameters to Python functions - the options you have - (2011-05-07)
[3459] Catching the fishes first? - (2011-09-27)
[3464] Passing optional and named parameters to python methods - (2011-10-04)
[3472] Static variables in functions - and better ways using objects - (2011-10-10)
[3474] Python Packages - groupings of modules. An introduction - (2011-10-11)
[3662] Finding all the unique lines in a file, using Python or Perl - (2012-03-20)
[3695] Functions are first class variables in Lua and Python - (2012-04-13)
[3766] Python timing - when to use a list, and when to use a generator - (2012-06-16)
[3852] Static variables in Python? - (2012-08-29)
[3885] Default local - a good choice by the author of Python - (2012-10-08)
[3931] Optional positional and named parameters in Python - (2012-11-23)
[3945] vargs in Python - how to call a method with unknown number of parameters - (2012-12-06)
[4029] Exception, Lambda, Generator, Slice, Dict - examples in one Python program - (2013-03-04)
[4161] Python varables - checking existance, and call by name or by value? - (2013-08-27)
[4212] Python functions - an introduction to how they work - (2013-11-16)
[4361] Multiple yields and no loops in a Python generator? - (2014-12-22)
[4407] Python - even named code blocks are objects - (2015-01-28)
[4410] A good example of recursion - a real use in Python - (2015-02-01)
[4448] What is the difference between a function and a method? - (2015-03-04)
[4645] What are callbacks? Why use them? An example in Python - (2016-02-11)
[4662] Recursion in Python - the classic example - (2016-03-07)
[4719] Nesting decorators - (2016-11-02)
[4722] Embedding more complex code into a named block - (2016-11-04)
[4724] From and Import in Python - where is the module loaded from? - (2016-11-06)
Some other Articles
The music of the stock marketA life lesson from the accuracy of numbers in Excel and LuaCommunity Area Partnership - inaugural AGMAdmissionGood example of recursion in Python - analyse an RSS feedI almost put the bins out this morningLearning to program in ...Melksham manslaughter case concludes - sort ofMonday night, Tuesday nightSimples