I am not sure what I am doing wrong.How to prevent the Test class to accept & throw error, when input of different types are passed.I am using Python 3.9.2
from dataclasses import dataclass, fields@dataclassclass Test:a: str = 'a'b: int = 1t = Test(2, 'b')print(fields(t))print(type(t.a))print(type(t.b))# output# (venv) D:\Playground>python dataClassesTest.py# (Field(name='a',type=<class 'str'>,default='a',default_factory=<dataclasses._MISSING_TYPE object at 0x00000232952D5880>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),_field_type=_FIELD), Field(name='b',type=<class 'int'>,default=1,default_factory=<dataclasses._MISSING_TYPE object at 0x00000232952D5880>,init=True,repr=True,hash=None,compare=True,metadata=mappingproxy({}),_field_type=_FIELD))# <class 'int'># <class 'str'>Best Answer
This can be solved by adding a __post_init__ method to your dataclass where you can check the types
(Based on this solution, with some corrections)
def __post_init__(self):for f in fields(type(self)):if not isinstance(getattr(self, f.name), f.type):current_type = type(getattr(self, f.name))raise TypeError(f"The field `{f.name}` was assigned by `{current_type}` instead of `{f.type}`")Note that this code doesn't work when importing
from __future__ import annotationsBecause then the type field in dataclasses.Field becomes a string