How to get instance variables in Python

Question

Is there a built-in method in Python to get an array of all a class  instance variables  For example  if I have this code   class hi    def   init   self       self ii    foo      self kk    bar    Is there a way for me to do this    gt  gt  gt  mystery method hi    ii    kk     Edit  I originally had asked for class variables erroneously

User · Answer

Suggest   gt  gt  gt  print vars   doc   vars  object   - gt  dictionary  Without arguments  equivalent to locals    With an argument  equivalent to object   dict      In otherwords  it essentially just wraps   dict

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built on dmark s answer to get the following  which is useful if you want the equiv of sprintf and hopefully will help someone     def sprint object       result          for i in  v for v in dir object  if not callable getattr object  v   and v 0                   result      n s     i   str getattr object  i           return result

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Both the Vars   and dict methods will work for the example the OP posted  but they won t work for  loosely  defined objects like   class foo    a    foo    b    bar    To print all non-callable attributes  you can use the following function   def printVars object       for i in  v for v in dir object  if not callable getattr object v             print   n s     i         exec  print object  s n n     i

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Sometimes you want to filter the list based on public private vars   E g   def pub vars self          Gives the variable names of our instance we want to expose             return  k for k in vars self  if not k startswith

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Use vars    class Foo object       def   init   self           self a   1         self b   2  vars Foo        gt    a   1   b   2  vars Foo    keys       gt    a    b

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Your example shows  instance variables    not really class variables   Look in hi obj   class     dict   items   for the class variables  along with other other class members like member functions and the containing module   class Hi  object        class var     23   skidoo      class variable     def   init    self            self ii    foo    instance variable         self jj    bar    Class variables are shared by all instances of the class

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You can also test if an object has a specific variable with    gt  gt  gt  hi obj   hi    gt  gt  gt  hasattr hi obj   some attribute

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Every object has a   dict   variable containing all the variables and its values in it   Try this   gt  gt  gt  hi obj   hi    gt  gt  gt  hi obj   dict   keys

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Although not directly an answer to the OP question  there is a pretty sweet way of finding out what variables are in scope in a function  take a look at this code    gt  gt  gt  def f x  y       z   x  2   y  2     sqrt z   z   5     return sqrt z   gt  gt  gt  f func code co varnames   x    y    z    sqrt z    gt  gt  gt     The func code attribute has all kinds of interesting things in it  It allows you todo some cool stuff  Here is an example of how I have have used this   def exec command self  cmd  msg  sig        def message msg           a   self link process self link recieved message msg           self exec command  a       def error msg           self printer printInfo msg       def set usrlist msg           self client connected users   msg      def chatmessage msg           self printer printInfo msg       if not locals   has key cmd   return     cmd   locals   cmd       try          if  sig  in cmd func code co varnames and                           msg  in cmd func code co varnames               cmd msg  sig          elif  msg  in cmd func code co varnames               cmd msg          else              cmd       except Exception  e          print   n-----------ERROR-----------          print  error     e         print  Error proccessing     cmd   name           print  Message     msg         print  Sig     sig         print  -----------ERROR----------- n

User · Answer

You normally can t get instance attributes given just a class  at least not without instantiating the class  You can get instance attributes given an instance  though  or class attributes given a class  See the  inspect  module  You can t get a list of instance attributes because instances really can have anything as attribute  and -- as in your example -- the normal way to create them is to just assign to them in the   init   method   An exception is if your class uses slots  which is a fixed list of attributes that the class allows instances to have  Slots are explained in http   www python org 2 2 3 descrintro html  but there are various pitfalls with slots  they affect memory layout  so multiple inheritance may be problematic  and inheritance in general has to take slots into account  too

User · Answer

You will need to first  examine the class  next  examine the bytecode for functions  then  copy the bytecode  and finally  use the   code   co varnames  This is tricky because some classes create their methods using constructors like those in the types module  I will provide code for it on GitHub

[python] How to get instance variables in Python?

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