About
How can we efficiently assign values to member variables? Using __annotations__ is one approach, but dataclasses or Pydantic’s BaseModel might offer better solutions.
class Example:
a: int
b: str = "default"
c: float
def __init__(self, c: float):
self.c = c
# check __annotations__ of a class
print("Class __annotations__:", Example.__annotations__)
# {'a': <class 'int'>, 'b': <class 'str'>, 'c': <class 'float'>}
def add_numbers(x: int, y: int) -> int:
return x + y
# check __annotations__ of a function
print("Function __annotations__:", add_numbers.__annotations__)
# {'x': <class 'int'>, 'y': <class 'int'>, 'return': <class 'int'>}
dataclass
from dataclasses import dataclass, fields, Field
@dataclass
class MyDataClass:
a: int = 10
b: str = "default"
c: float = 3.14
@classmethod
def from_defaults(cls, **kwargs):
defaults = {f.name: f.default for f in fields(cls) if f.default is not Field.default}
# overwrite defaults by `kwargs`
combined = {**defaults, **kwargs}
return cls(**combined)
obj1 = MyDataClass.from_defaults()
print(obj1) # MyDataClass(a=10, b='default', c=3.14)
obj2 = MyDataClass.from_defaults(a=20, c=1.23)
print(obj2) # MyDataClass(a=20, b='default', c=1.23)
