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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.
Passing a variable number of parameters in to a function / method

How many columns are there in each row in a table? It will vary, depending on the table!

If I want to write a "row" function in PHP, passing in as parameters each of my columns, I don't know the parameter count. But I can find out using the fun_num_args function, and I can then get each of them using the func_get_arg function.

Here's an example:
  function row() {
    $res = "<tr>";
    for ($k=0; $k<func_num_args(); $k++) {
      $res .= func_get_arg($k);
    }
    $res .= "</tr>";
    return $res;
  }


In Python, you can collect a variable number of arguments using a * in the def of the function / method, such as
  def row(*eachcol):
and indeed you could collect named arguments into a dictionary using **.

In Perl, you can check how many arguments you have using $#_, or using @_ in a scalar content

And in Tcl, a final argument called args in a proc definition will "sponge up" all remaining parameters, no matter how many of them there are.
  proc ceiling {limit args} {

One slight word of caution - it's often much better to pass an array or a list into a function than a variable number of arguments. But if you do need to pass them individually, then the tips above will point you in the right direction for Perl, PHP, Python and Tcl.
(written 2010-08-20)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
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)
  [2506] Good example of recursion in Python - analyse an RSS feed - (2009-11-18)
  [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)
  [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)
  [4441] Reading command line parameters in Python - (2015-02-23)
  [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)

T207 - Tcl/Tk - Procedures and Variable Scope
  [122] Passing arrays to procs in Tcl - (2004-11-18)
  [409] Functions and commands with dangerous names - (2005-08-11)
  [1404] Tcl - global, upvar and uplevel. - (2007-10-24)
  [1782] Calling procs in Tcl and how it compares to Perl - (2008-09-02)
  [2466] Tcl - passing arrays and strings in and back out of procs - (2009-10-22)
  [2476] Tcl - uplevel to run code at calling level - (2009-10-24)
  [3192] Tcl - Some example of HOW TO in handling data files and formats - (2011-03-04)
  [3414] Passing back multiple results in Tcl - upvar and uplevel - (2011-09-01)
  [3629] Sharing lots of values in Tcl without having lots of global declarations - (2012-02-28)
  [4398] Accessing variables across subroutine boundaries - Perl, Python, Java and Tcl - (2015-01-18)

P209 - Subroutines in Perl
  [357] Where do Perl modules load from - (2005-06-24)
  [531] Packages in packages in Perl - (2005-12-16)
  [588] Changing @INC - where Perl loads its modules - (2006-02-02)
  [969] Perl - $_ and @_ - (2006-12-07)
  [1826] Perl - Subs, Chop v Chomp, => v , - (2008-10-08)
  [1850] Daisy the Cow and a Pint of Ginger Beer - (2008-10-21)
  [1860] Seven new intermediate Perl examples - (2008-10-30)
  [1921] Romeo and Julie - (2008-12-04)
  [2069] Efficient calls to subs in Perl - avoid duplication, gain speed - (2009-03-07)
  [2550] Do not copy and paste code - there are much better ways - (2009-12-26)
  [2833] Fresh Perl Teaching Examples - part 2 of 3 - (2010-06-27)
  [3066] Separating groups of variables into namespaces - (2010-11-24)
  [3574] Perl functions such as chop change their input parameters - (2012-01-10)
  [3833] Learning to use existing classes in Perl - (2012-08-10)

H105 - PHP - Functions
  [223] There is a function in PHP to do that - (2005-02-21)
  [339] Passing information into and out of PHP functions - (2005-06-07)
  [421] Don't repeat code - use loops or functions - (2005-08-21)
  [866] A lazy programmer is a good programmer - (2006-09-15)
  [936] Global, Superglobal, Session variables - scope and persistance in PHP - (2006-11-21)
  [1021] PHP - static declaration - (2007-01-04)
  [1267] is there a lookup function in php? - (2007-07-15)
  [1357] Clean my plate, but keep my wine bottle. (PHP; Static) - (2007-09-18)
  [1380] Static variables in PHP - (2007-10-05)
  [2488] A variable number of arguments in a PHP function - (2009-11-02)
  [2630] Static variables and ampersands in PHP - (2010-02-10)
  [2682] Adding extensions to PHP Open Source applications - callbacks - (2010-03-17)
  [2737] Improving your function calls (APIs) - General and PHP - (2010-04-24)
  [3026] Coding efficiency - do not repeat yourself! - (2010-11-02)


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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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