CODEWITHSUNDEEP
pythonclasserror-handling
Jayden Rice
Jayden Rice

Reputation: 301

How to check if a variable is float or int?

When I construct a __init__() in a Car class, say, I want to check that variables make and current_gas to be string and float or integer (not negative), respectively.

Then how do I raise an appropriate error for each variable?

I tried

class Car:
    def __init__(self,make,current_gas):
        if type(make) != str:
            raise TypeError("Make should be a string")
        if not type(current_gas) == float or type(current_gas) == int:
            raise TypeError("gas amount should be float or int")
        if current_gas <=0:
            raise ValueError("gas amount should not be negative")

However, this __init__() is not working properly. How do I fix it?

Upvotes: 1

Views: 872

Answers (1)

flakes
flakes

Reputation: 23634

Looks like your boolean logic on the second if statement is wrong (not needs to be around both checks), however, you can use isinstance to simplify checking multiple types.

You also used current_gas_level instead of current_gas. Try something like this:

class Car:
    def __init__(self, make, current_gas):
        if not isinstance(make, str):
            raise TypeError("Make should be a string")
        if not isinstance(current_gas, (int, float)):
            raise TypeError("gas amount should be float or int")
        if current_gas <= 0:
            raise ValueError("gas amount should not be negative")

        self.make = make
        self.current_gas = current_gas

To make the definition a little easier to follow, I might also suggest using a dataclass and a __post_init__ to do the validation.

from dataclasses import dataclass
from typing import Union


@dataclass
class Car:
    make: str
    current_gas: Union[int, float]

    def __post_init__(self):
        if not isinstance(self.make, str):
            raise TypeError("Make should be a string")
        if not isinstance(self.current_gas, (int, float)):
            raise TypeError("gas amount should be float or int")
        if self.current_gas <= 0:
            raise ValueError("gas amount should not be negative")

Upvotes: 4

Related Questions