How can I access static class variables within class methods in Python

Question

If I have the following python code   class Foo object       bar   1      def bah self           print bar   f   Foo   f bah     It complains   NameError  global name  bar  is not defined   How can I access class static variable bar within method bah

User · Answer

class Foo object        bar   1      def bah self            print Foo bar  f   Foo    f bah

User · Answer

As with all good examples  you ve simplified what you re actually trying to do   This is good  but it is worth noting that python has a lot of flexibility when it comes to class versus instance variables  The same can be said of methods   For a good list of possibilities  I recommend reading Michael F  tsch  new-style classes introduction  especially sections 2 through 6   One thing that takes a lot of work to remember when getting started is that python is not java   More than just a cliche   In java  an entire class is compiled  making the namespace resolution real simple  any variables declared outside a method  anywhere  are instance  or  if static  class  variables and are implicitly accessible within methods   With python  the grand rule of thumb is that there are three namespaces that are searched  in order  for variables    The function method The current module Builtins    begin pedagogy   There are limited exceptions to this   The main one that occurs to me is that  when a class definition is being loaded  the class definition is its own implicit namespace   But this lasts only as long as the module is being loaded  and is entirely bypassed when within a method   Thus    gt  gt  gt  class A object           foo    foo          bar   foo    gt  gt  gt  A foo  foo   gt  gt  gt  A bar  foo    but    gt  gt  gt  class B object           foo    foo          def get foo                return foo         bar   get foo      Traceback  most recent call last     File   lt pyshell 11 gt    line 1  in  lt module gt      class B object     File   lt pyshell 11 gt    line 5  in B     bar   get foo     File   lt pyshell 11 gt    line 4  in get foo     return foo NameError  global name  foo  is not defined    end pedagogy   In the end  the thing to remember is that you do have access to any of the variables you want to access  but probably not implicitly   If your goals are simple and straightforward  then going for Foo bar or self bar will probably be sufficient   If your example is getting more complicated  or you want to do fancy things like inheritance  you can inherit static class methods    or the idea of referring to the name of your class within the class itself seems wrong to you  check out the intro I linked

User · Answer

Instead of bar use self bar or Foo bar  Assigning to Foo bar will create a static variable  and assigning to self bar will create an instance variable

User · Answer

bar is your static variable and you can access it using Foo bar  Basically  you need to qualify your static variable with Class name

User · Answer

class Foo object           bar   1      def bah object reference           object reference var   Foo bar         return object reference var   f   Foo    print  var    f bah

User · Answer

Define class method   class Foo object       bar   1      classmethod     def bah cls               print cls bar   Now if bah   has to be instance method  i e  have access to self   you can still directly access the class variable   class Foo object       bar   1     def bah self               print self bar

[python] How can I access "static" class variables within class methods in Python?

Examples related to python

Examples related to oop

Examples related to static-variables