Understanding 'Self' and Python instance creation

[WalidKhan]

I'm attempting to understand 'self' in Python on a deeper level since I find myself not fully comprehending it when I use it.

Consider the following code:

class FoodItems:

def __init__(self, other arguments):
some code

def main():
some code

item1 = FoodItems
item1.main()

For the [def main()] function I'm not passing the 'Self' argument in it, yet the code works when I call it. After reading this post, my understanding of 'Self' is that it must be provided every time a method is defined under the class. I receive the error (missing 1 needed positional argument:'self') if I pass 'Self' and then call the method.

Could someone please clarify this to me? When it comes to generating instances, I can't discern the difference between calling an instance with or without brackets, such as (item1 = FoodItems vs. item1=FoodItems()).

When I use parentheses, I receive the error "missing 8 required positional arguments that were initialized in the constructor."

Any assistance would be highly appreciated; thank you in advance!
 

[Sensei]

"self" does not have to be called self in Python. It can be anything that is not a reserved word.

"self" is the Python equivalent of "this" from other languages such as C++ or Java:

https://en.wikipedia.org/wiki/This_(computer_programming)

 

In other words, it is a pointer/holder/reference to the object's data. Each new instance will have a different set of data, pointed to by "this"/"self".

 

https://www.w3schools.com/python/gloss_python_self.asp

class Person:
  def __init__(mysillyobject, name, age):
    mysillyobject.name = name
    mysillyobject.age = age

  def myfunc(abc):
    print("Hello my name is " + abc.name)

p1 = Person("John", 36)
p1.myfunc() 

"mysillyobject" and "abc" are equal to "p1" in the above code.

 

The above code in C++ could look like:

#include <iostream>

class Person {
 private:
  std::string name;
  int age;
 public: Person( const std::string name, int age ) {
  this->name = name;
  this->age = age;
 }
 public: void myfunc() {
  std::cout << "Name: " << this->name << std::endl;
  std::cout << "Age: " << this->age << std::endl;
 }
};

int main() {
 Person *p = new Person( "John", 36 );
 p->myfunc();
 return( 0 );
}

C++ allows you to omit "this". "this" is the default for the object's local variables (i.e. name and age). But since I used these words as constructor parameters, I have to use "this" to differentiate them.

I could write:

 public: void myfunc() {
  std::cout << "Name: " << name << std::endl;
  std::cout << "Age: " << age << std::endl;
 }

And the C++ compiler would know that "name" is equivalent to "this->name", and "age" is equivalent to "this->age".

It's different in Python and "self" is obligatory.