Each time you call a function, you start off with a fresh set of variables. That's usually exactly what you want, as you don't usually want one calculation to be influenced by the debris of the previous similar calculation.
In Python, you can define a variable as an attribute of the method (using methodname-dot in front of the name) so that it remains / is retained. That's the equivalent of marking a variable
static in PHP.
Here's the code for a counter which keeps a tally of the number of times a method has been called:
def tick():
tick.count += 1
You'll either need to initialise the attribute outside the method (but after you have defined the method), or catch the exception that's thrown when you try to increment a variable that doesn't exist the first time. Full source code is
[here].
Example from this week's
Python course.
(written 2012-08-29, updated 2012-09-01)
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)
[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)
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