Built-in Methods

Instance Method vs Static Method

Instance Methods (normal methods without declaring @) specifies with that particular declared instance. For ex. a unique event is specific to a specific calendar instance, and should not exist on other calendar instances.  

Static Method doesn't care about any particular instance. For ex, a weekend on a calendar applies to all calendars since it is universally agreed upon how calendars work, regardless of instance

Also look into Class Method if need to consider inheritance. 

class Calendar:
    def __init__(self):
        self.events = []

    def add_event(self, event):
        self.events.append(event)

    @staticmethod
    def is_weekend(dt):
        pass

Dataclasses

Without using Dataclass, 

• If you print, it will be the memory address where the object resides.
  •  To print a string, will have to modify the _str_ dunder method 
• A new object with identical information will be a new object

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

person1 = Person("Geralt", "Witcher", 30)
person2 = Person("Yennefer", "Sorceress", 25)
person3 = Person("Yennefer", "Sorceress", 25)

print(id(person2))
print(id(person3))
print(person1)

print(person3 == person2)



"""
OUTPUT: 
140244722433808
140244722433712
<__main__.Person object at 0x7f8d44dcbfd0>
False
"""

With Dataclass:

• Print string information instead of object, unless using id()
• A new object will still be a new object, but if information is identical it will it will return True 

from dataclasses import dataclass, field

@dataclass(order=True,frozen=False)
class Person:
    sort_index: int = field(init=False, repr=False)
    name: str
    job: str
    age: int
    strength: int = 100

    def __post_init__(self):
        object.__setattr__(self, 'sort_index', self.strength)

    def __str__(self):
        return f'{self.name}, {self.job} ({self.age})'


person1 = Person("Geralt", "Witcher", 30, 99)
person2 = Person("Yennefer", "Sorceress", 25)
person3 = Person("Yennefer", "Sorceress", 25)

print(person1)
print(id(person2))
print(id(person3))
print(person3 == person2)
print(person1 > person2)

"""
Geralt, Witcher (30)
140120080908048
140120080907856
True
False
"""