Question

i am learning classes in python and i found some functions called magic methods or special methods that we use them inside the class definitions , the question is the following :

if we add double underlines before and after any original built in function , does that allow us to use all them inside a class to do the same task , for example .

>>> int (3.6)
3

>>> str(3.7)
'3.7'

and we can use str in class as following :

class Character:
    def __init__(self, name, initial_health):
       self.name = name
       self.health = initial_health
       self.inventory = []

    def __str__(self):
       s  = "Name: " + self.name
       s += " Health: " + str(self.health)
       s += " Inventory: " + str(self.inventory)
       return s

   def grab(self, item):
       self.inventory.append(item)

   def get_health(self):
       return self.health

   def example():
       me = Character("Bob", 20)
       print str(me)
       me.grab("pencil")
       me.grab("paper")
       print str(me)
       print "Health:", me.get_health()

example()

the result :

Name: Bob Health: 20 Inventory: []
Name: Bob Health: 20 Inventory: ['pencil', 'paper']
Health: 20

is all built in functions can be magic (special) functions ?

thanks.

Answer 1

No. Some built-in functions have a special method for them, some don’t. Also some special methods don’t correspond to a built-in function, and some built-in functions make use of a special method with a different name (e.g., __instancecheck__). You can see which special methods there are in the documentation. This is also a good reference site.