Change class attribute type from string to int-CodePudding

I have this class that should be initialized with all parameter int but sometimes it gets string instead of int

@dataclass
class Meth:
    one: Optional[int] = None
    two: Optional[int] = None
    three: Optional[int] = None


my_class = Meth(one="1",two=2,three=None)

As you can see in attribute one there is bad type. And to fix this my first thought was to create it again like this

new_class = Meth(one=int(my_class.one),two=int(my_class.two),three=int(my_class.three)

but I get this error because three is None

TypeError: int() argument must be a string, a bytes-like object, or a real number, not 'NoneType'

So my question is what would be the best way to change all attribute types to the correct type.

CodePudding user response：

The error is caused when converting None to int, not because of specified types. You can add a check:

new_class = Meth(
   one=int(my_class.one),
   two=int(my_class.two),
   three=my_class.three if my_class.three is None else int(my_class.three)
)

A better way would be to do it while initializing the class

class Meth:
    one: int = None
    def __init__(self, 
            one: Optional[Union[str,int]] = None,
            two: Optional[int] = None,
            three: Optional[int] = None):
    # Do the checks and assign values
    if one is not None:
        self.one = int(one)

Or by using a library for data validation, pydantic or alike:

from pydantic import BaseModel

class Meth(BaseModel):
    one: int
    two: Optional[int]
    three: Optional[int]

my_class = Meth(one="1",two=2,three=None)
assert type(my_class.one) is int