How do I pass a method as a parameter in Python

Question

Is it possible to pass a method as a parameter to a method   self method2 self method1   def method1 self       return  hello world   def method2 self  methodToRun       result   methodToRun call       return result

User · Answer

Example  a simple function call wrapper  def measure cpu time f   args       t start   time process time       ret   f  args      t end   time process time       return t end - t start  ret

User · Answer

Yes it is possible  Just call it   class Foo object       def method1 self           pass     def method2 self  method           return method    foo   Foo   foo method2 foo method1

User · Answer

Yes  functions  and methods  are first class objects in Python  The following works   def foo f       print  Running parameter f         f    def bar        print  In bar      foo bar    Outputs   Running parameter f    In bar      These sorts of questions are trivial to answer using the Python interpreter or  for more features  the IPython shell

User · Answer

Methods are objects like any other  So you can pass them around  store them in lists and dicts  do whatever you like with them  The special thing about them is they are callable objects so you can invoke   call   on them    call   gets called automatically when you invoke the method with or without arguments so you just need to write methodToRun

User · Answer

If you want to pass a method of a class as an argument but don t yet have the object on which you are going to call it  you can simply pass the object once you have it as the first argument  i e  the  self  argument    class FooBar       def   init   self  prefix           self prefix   prefix      def foo self  name           print   s  s     self prefix  name    def bar some method       foobar   FooBar  Hello       some method foobar   World    bar FooBar foo    This will print  Hello World

User · Answer

Here is your example re-written to show a stand-alone working example   class Test      def method1 self           return  hello world       def method2 self  methodToRun           result   methodToRun           return result      def method3 self           return self method2 self method1   test   Test    print test method3

User · Answer

Not exactly what you want  but a related useful tool is getattr    to use method s name as a parameter   class MyClass     def   init   self         pass    def MyMethod self         print  Method ran      Create an object object   MyClass     Get all the methods of a class method list    func for func in dir MyClass  if callable getattr MyClass  func      You can use any of the methods in method list    MyMethod  is the one we want to use right now    This is the same as running  object MyMethod    getattr object  MyMethod

User · Answer

Lots of good answers but strange that no one has mentioned using a lambda function   So if you have no arguments  things become pretty trivial   def method1        return  hello world   def method2 methodToRun       result   methodToRun       return result  method2 method1    But say you have one  or more  arguments in method1    def method1 param       return  hello     str param   def method2 methodToRun       result   methodToRun       return result   Then you can simply invoke method2 as method2 lambda  method1  world       method2 lambda  method1  world     gt  gt  gt  hello world method2 lambda  method1  reader     gt  gt  gt  hello reader   I find this much cleaner than the other answers mentioned here

User · Answer

Yes it is  just use the name of the method  as you have written  Methods and functions are objects in Python  just like anything else  and you can pass them around the way you do variables  In fact  you can think about a method  or function  as a variable whose value is the actual callable code object  Since you asked about methods  I m using methods in the following examples  but note that everything below applies identically to functions  except without the self parameter   To call a passed method or function  you just use the name it s bound to in the same way you would use the method s  or function s  regular name  def method1 self       return  hello world   def method2 self  methodToRun       result   methodToRun       return result  obj method2 obj method1   Note  I believe a   call     method does exist  i e  you could technically do methodToRun   call      but you probably should never do so explicitly    call     is meant to be implemented  not to be invoked from your own code  If you wanted method1 to be called with arguments  then things get a little bit more complicated  method2 has to be written with a bit of information about how to pass arguments to method1  and it needs to get values for those arguments from somewhere  For instance  if method1 is supposed to take one argument  def method1 self  spam       return  hello     str spam   then you could write method2 to call it with one argument that gets passed in  def method2 self  methodToRun  spam value       return methodToRun spam value   or with an argument that it computes itself  def method2 self  methodToRun       spam value   compute some value       return methodToRun spam value   You can expand this to other combinations of values passed in and values computed  like def method1 self  spam  ham       return  hello     str spam      and     str ham   def method2 self  methodToRun  ham value       spam value   compute some value       return methodToRun spam value  ham value   or even with keyword arguments def method2 self  methodToRun  ham value       spam value   compute some value       return methodToRun spam value  ham ham value   If you don t know  when writing method2  what arguments methodToRun is going to take  you can also use argument unpacking to call it in a generic way  def method1 self  spam  ham       return  hello     str spam      and     str ham   def method2 self  methodToRun  positional arguments  keyword arguments       return methodToRun  positional arguments    keyword arguments   obj method2 obj method1    spam      ham    ham     In this case positional arguments needs to be a list or tuple or similar  and keyword arguments is a dict or similar  In method2 you can modify positional arguments and keyword arguments  e g  to add or remove certain arguments or change the values  before you call method1

[python] How do I pass a method as a parameter in Python

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