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Variable storage - Perl, Tcl and Python compared

Variable storage - Perl, Python, TclFrom Monday to Wednesday, I was teaching Python to a group of delegates at a company where I have previously taught Tcl and Expect and Perl. And this interesting diagram shows just what a contrast there is between the three languages right from the start - in terms of how data is stored into variables!

In Tcl, all data is stored a strings so the number 21 would be 2 bytes - the character 2 followed by the character 1.

In Perl, you have a much more 'traditional' model where the name of the variable - which has a leading $ - may be considered to be a direct label on the storage element

And in Python, everything is an object, so your variable name contains a reference to a location on the heap at which the data is stored.

(written 2009-10-08)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
P202 - Perl Fundamentals
  [3917] BODMAS - the order a computer evaluates arithmetic expressions - (2012-11-09)
  [3574] Perl functions such as chop change their input parameters - (2012-01-10)
  [3542] What order are operations performed in, in a Perl expression? - (2011-12-07)
  [3398] Perl - making best use of the flexibility, but also using good coding standards - (2011-08-19)
  [3329] Perl from basics - (2011-06-20)
  [3278] Do I need to initialise variables - programming in C, C++, Perl, PHP, Python, Ruby or Java. - (2011-05-05)
  [3102] AND and OR operators - what is the difference between logical and bitwise varieties? - (2010-12-24)
  [3059] Object Orientation in an hour and other Perl Lectures - (2010-11-18)
  [2876] Different perl examples - some corners I rarely explore - (2010-07-18)
  [2832] Are you learning Perl? Some more examples for you! - (2010-06-27)
  [1946] Variable Types in Perl - (2008-12-15)
  [1826] Perl - Subs, Chop v Chomp, => v , - (2008-10-08)
  [1726] Hot Courses - Perl - (2008-07-28)
  [1448] Question on division (Java) - Also Perl, PHP, Python ... - (2007-11-28)
  [1312] Some one line Perl tips and techniques - (2007-08-21)
  [748] Getting rid of variables after you have finished with them - (2006-06-06)
  [184] MTBF of coffee machines - (2005-01-20)

T202 - Tcl/Tk - Tcl Fundamentals
  [1469] Curley brackets v double quotes - Tcl, Tk, Expect - (2007-12-12)
  [1426] Buffering up in Tcl - the empty coke can comparison - (2007-11-10)
  [1282] Stringing together Tcl scripts - (2007-07-29)
  [1136] Buffering output - why it is done and issues raised in Tcl, Perl, Python and PHP - (2007-04-06)
  [782] Converting between Hex and Decimal in Tcl - (2006-06-28)
  [362] The ireallyreallywanna operator - (2005-06-28)
  [349] Comments in Tcl - (2005-06-16)
  [328] Making programs easy for any user to start - (2005-05-29)
  [210] Joining lists in Tcl. Indirect variables in Tcl. - (2005-02-12)
  [3] Looking for a donkey - (2004-08-05)

Y102 - Python - Fundamentals
  [3886] Formatting output - why we need to, and first Python example - (2012-10-09)
  [3551] Some terms used in programming (Biased towards Python) - (2011-12-12)
  [3181] Beware - a=a+b and a+=b are different - Python - (2011-02-23)
  [3083] Python - fresh examples from recent courses - (2010-12-11)
  [2778] Learning to program in Python 2 ... and / or in Python 3 - (2010-05-24)
  [2368] Python - fresh examples of all the fundamentals - (2009-08-20)
  [1878] Pascals Triangle in Python and Java - (2008-11-10)
  [1461] Python - input v raw input - (2007-12-06)
  [1430] Integer v float - Python - (2007-11-12)
  [956] Python security - trouble with input - (2006-11-30)
  [633] Copying a reference, or cloning - (2006-03-05)


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