Python: How to avoid explicit 'self'?

Question

I have been learning Python by following some pygame tutorials.

Therein I found extensive use of the keyword self, and coming from a primarily Java background, I find that I keep forgetting to type self. For example, instead of self.rect.centerx I would type rect.centerx, because, to me, rect is already a member variable of the class.

The Java parallel I can think of for this situation is having to prefix all references to member variables with this.

Am I stuck prefixing all member variables with self, or is there a way to declare them that would allow me to avoid having to do so?

Even if what I am suggesting isn't pythonic, I'd still like to know if it is possible.

I have taken a look at these related SO questions, but they don't quite answer what I am after:

• Python - why use “self” in a class?
• Why do you need explicitly have the “self” argument into a Python method?

Answer 1

self is part of the python syntax to access members of objects, so I'm afraid you're stuck with it

Answer 2

yes, you must always specify self, because explicit is better than implicit, according to python philosophy.

You will also find out that the way you program in python is very different from the way you program in java, hence the use of self tends to decrease because you don't project everything inside the object. Rather, you make larger use of module-level function, which can be better tested.

by the way. I hated it at first, now I hate the opposite. same for indented-driven flow control.

Answer 3

Actually self is not a keyword, it's just the name conventionally given to the first parameter of instance methods in Python. And that first parameter can't be skipped, as it's the only mechanism a method has of knowing which instance of your class it's being called on.

Answer 4

Python requires specifying self. The result is there's never any confusion over what's a member and what's not, even without the full class definition visible. This leads to useful properties, such as: you can't add members which accidentally shadow non-members and thereby break code.

One extreme example: you can write a class without any knowledge of what base classes it might have, and always know whether you are accessing a member or not:

class A(some_function()):
  def f(self):
    self.member = 42
    self.method()

That's the complete code! (some_function returns the type used as a base.)

Another, where the methods of a class are dynamically composed:

class B(object):
  pass

print B()
# <__main__.B object at 0xb7e4082c>

def B_init(self):
  self.answer = 42
def B_str(self):
  return "<The answer is %s.>" % self.answer
# notice these functions require no knowledge of the actual class
# how hard are they to read and realize that "members" are used?

B.__init__ = B_init
B.__str__ = B_str

print B()
# <The answer is 42.>

Remember, both of these examples are extreme and you won't see them every day, nor am I suggesting you should often write code like this, but they do clearly show aspects of self being explicitly required.

Answer 5

You can use whatever name you want, for example

class test(object):
    def function(this, variable):
        this.variable = variable

or even

class test(object):
    def function(s, variable):
        s.variable = variable

but you are stuck with using a name for the scope.

I do not recommend you use something different to self unless you have a convincing reason, as it would make it alien for experienced pythonistas.