Although it would be convenient at times to be able to refer to any variable anywhere in your program, this is not how most languages work by default. And they're designed that way! That's to avoid confusion as a program grows, when there's a strong possibility of several programmers on the same project happening to choose the same name to use within their own are (module / function / subroutine). It also makes for cleaner code, as it avoids anyone who's writing or updating the program being tempted to make use of a variable from another area without passing it around properly - i.e. it avoids adding a long distance dependency that will be trouble during code maintenance.
Example in Python -
[here] - from yesterday's
learning to program in Python course.
(written 2012-10-08, updated 2012-10-13)
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)
[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)
[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)
Some other Articles
Melksham Chamber of Commerce - whence in 2013 and beyond?What a difference a year made - Melksham CampusInheritance, Composition and Associated objects - when to use which - Python exampleFormatting output - why we need to, and first Python exampleDefault local - a good choice by the author of PythonPictures - across the park, French Weir and River Tone, TauntonApple Pressing Day 2012Community Transport - Pewsey, Taunton, and the whole picture tooWiltshire Public Transport User Group co-ordinationChamber of Commerce - looking forward in Melksham and in Wessex