What is a method in Python

Question

Can anyone  please  explain to me in very simple terms what a  method  is in Python   The thing is in many Python tutorials for beginners this word is used in such way as if the beginner already knew what a method is in the context of Python  While I am of course familiar with the general meaning of this word  I have no clue what this term means in Python  So  please  explain to me what the  Pythonian  method is all about   Some very simple example code would be very much appreciated as a picture is worth thousand words

User · Answer

To understand methods you must first think in terms of object oriented programming: Let's take a car as a a class. All cars have things in common and things that make them unique, for example all cars have 4 wheels, doors, a steering wheel.... but Your individual car (Lets call it, my_toyota) is red, goes from 0-60 in 5.6s Further the car is currently located at my house, the doors are locked, the trunk is empty... All those are properties of the instance of my_toyota. your_honda might be on the road, trunk full of groceries ...

However there are things you can do with the car. You can drive it, you can open the door, you can load it. Those things you can do with a car are methods of the car, and they change a properties of the specific instance.

as pseudo code you would do:

my_toyota.drive(shop)

to change the location from my home to the shop or

my_toyota.load([milk, butter, bread]

by this the trunk is now loaded with [milk, butter, bread].

As such a method is practically a function that acts as part of the object:

class Car(vehicle)
    n_wheels = 4

    load(self, stuff):
    '''this is a method, to load stuff into the trunk of the car'''
        self.open_trunk
        self.trunk.append(stuff)
        self.close_trunk

the code then would be:

my_toyota = Car(red)
my_shopping = [milk, butter, bread]
my_toyota.load(my_shopping)

User · Answer

A method is a function that takes a class instance as its first parameter  Methods are members of classes   class C      def method self  possibly  other  arguments           pass   do something here   As you wanted to know what it specifically means in Python  one can distinguish between bound and unbound methods  In Python  all functions  and as such also methods  are objects which can be passed around and  played with   So the difference between unbound and bound methods is   1  Bound methods    Create an instance of C and call method   instance   C    print instance method   prints   lt bound method C method of  lt   main   C instance at 0x00FC50F8 gt  gt   instance method 1  2  3    normal method call  f   instance method f 1  2  3    method call without using the variable  instance  explicitly   Bound methods are methods that belong to instances of a class  In this example  instance method is bound to the instance called instance  Everytime that bound method is called  the instance is passed as first parameter automagically - which is called self by convention   2  Unbound methods  print C method   prints   lt unbound method C method gt   instance   C   C method instance  1  2  3    this call is the same as    f   C method f instance  1  2  3      this one     instance method 1  2  3    and the same as calling the bound method as you would usually do   When you access C method  the method inside a class instead of inside an instance   you get an unbound method  If you want to call it  you have to pass the instance as first parameter because the method is not bound to any instance   Knowing that difference  you can make use of functions methods as objects  like passing methods around  As an example use case  imagine an API that lets you define a callback function  but you want to provide a method as callback function  No problem  just pass self myCallbackMethod as the callback and it will automatically be called with the instance as first argument  This wouldn t be possible in static languages like C    or only with trickery    Hope you got the point    I think that is all you should know about method basics  You could also read more about the classmethod and staticmethod decorators  but that s another topic

User · Answer

If you think of an object as being similar to a noun  then a method is similar to a verb  Use a method right after an object  i e  a string or a list  to apply a method s action to it

User · Answer

http   docs python org 2 tutorial classes html method-objects     Usually  a method is called right after it is bound   x f         In the MyClass example  this will return the string  hello world     However  it is not necessary to call a method right away  x f is a   method object  and can be stored away and called at a later time  For   example   xf   x f while True      print xf         will continue to print hello world until the end of time       What exactly happens when a method is called  You may have noticed   that x f   was called without an argument above  even though the   function definition for f   specified an argument  What happened to   the argument  Surely Python raises an exception when a function that   requires an argument is called without any     even if the argument   isn   t actually used         Actually  you may have guessed the answer  the special thing about   methods is that the object is passed as the first argument of the   function  In our example  the call x f   is exactly equivalent to   MyClass f x   In general  calling a method with a list of n arguments   is equivalent to calling the corresponding function with an argument   list that is created by inserting the method   s object before the first   argument       If you still don   t understand how methods work  a look at the   implementation can perhaps clarify matters  When an instance attribute   is referenced that isn   t a data attribute  its class is searched  If   the name denotes a valid class attribute that is a function object  a   method object is created by packing  pointers to  the instance object   and the function object just found together in an abstract object    this is the method object  When the method object is called with an   argument list  a new argument list is constructed from the instance   object and the argument list  and the function object is called with   this new argument list

User · Answer

Sorry  but--in my opinion--RichieHindle is completely right about saying that method        It s a function which is a member of a class    Here is the example of a function that becomes the member of the class  Since then it behaves as a method of the class  Let s start with the empty class and the normal function with one argument    gt  gt  gt  class C          pass      gt  gt  gt  def func self           print  func called       gt  gt  gt  func  whatever   func called   Now we add a member to the C class  which is the reference to the function  After that we can create the instance of the class and call its method as if it was defined inside the class    gt  gt  gt  C func   func  gt  gt  gt  o   C    gt  gt  gt  o func   func called   We can use also the alternative way of calling the method    gt  gt  gt  C func o  func called   The o func even manifests the same way as the class method    gt  gt  gt  o func  lt bound method C func of  lt   main   C instance at 0x000000000229ACC8 gt  gt    And we can try the reversed approach  Let s define a class and steal its method as a function    gt  gt  gt  class A          def func self               print  aaa       gt  gt  gt  a   A    gt  gt  gt  a func  lt bound method A func of  lt   main   A instance at 0x000000000229AD08 gt  gt   gt  gt  gt  a func   aaa   So far  it looks the same  Now the function stealing    gt  gt  gt  afunc   A func  gt  gt  gt  afunc a  aaa       The truth is that the method does not accept  whatever  argument    gt  gt  gt  afunc  whatever   Traceback  most recent call last     File   lt stdin gt    line 1  in  lt module gt  TypeError  unbound method func   must be called with A instance as first    argument  got str instance instead    IMHO  this is not the argument against method is a function that is a member of a class   Later found the Alex Martelli s answer that basically says the same  Sorry if you consider it duplication

User · Answer

It s a function which is a member of a class  class C      def my method self           print  quot I am a C quot    c   C   c my method      Prints  quot I am a C quot    Simple as that   There are also some alternative kinds of method  allowing you to control the relationship between the class and the function   But I m guessing from your question that you re not asking about that  but rather just the basics

User · Answer

In Python  a method is a function that is available for a given object because of the object s type   For example  if you create my list    1  2  3   the append method can be applied to my list because it s a Python list  my list append 4   All lists have an append method simply because they are lists   As another example  if you create my string    some lowercase text   the upper method can be applied to my string simply because it s a Python string  my string upper     Lists don t have an upper method  and strings don t have an append method  Why  Because methods only exist for a particular object if they have been explicitly defined for that type of object  and Python s developers have  so far  decided that those particular methods are not needed for those particular objects   To call a method  the format is object name method name    and any arguments to the method are listed within the parentheses  The method implicitly acts on the object being named  and thus some methods don t have any stated arguments since the object itself is the only necessary argument  For example  my string upper   doesn t have any listed arguments because the only required argument is the object itself  my string   One common point of confusion regards the following   import math math sqrt 81    Is sqrt a method of the math object  No  This is how you call the sqrt function from the math module  The format being used is module name function name    instead of object name method name    In general  the only way to distinguish between the two formats  visually  is to look in the rest of the code and see if the part before the period  math  my list  my string  is defined as an object or a module

[python] What is a "method" in Python?

Examples related to python

Examples related to methods