If I design a function like
def f(a, b):
...
a must be in [1,2,3]. If I pass 4 to parameter a, it should raise an exception. Is there a pythonic way to limit the value range of a function argument?
Added
Please note, is there a more pythonic way to implement it? Not just a simple assert or if in.
For instance, decorator or maybe some syntactic sugar.
>Solution :
Yes, and also you can raise an exception if the input value is outside the desired range. For example, let’s say you have a function called f that takes two integer parameters, a and b. To limit the range of a, you can use an annotation like a: int to specify that a should be an integer. Then, you can add an if statement to check if a is within the desired range. If it’s not, a ValueError will be raised with a specific error message. So, if you call the function with an invalid value for a, like 4, it will raise an exception.
def f(a: int, b: int) -> int:
if a not in [1, 2, 3]:
raise ValueError("Invalid value for 'a'. Expected 1, 2, or 3.")
#rest of your functions
return result
update
In this new example, I created a decorator called value_range that you can use to limit the range of a function argument, and it’s super easy to use, just apply the decorator to your function f and specify the range values you want, as you see if you pass a value outside that range, it’ll raise a ValueError. It’s a really neat and pythonic way to keep things in check without messy assert or if statements!
from typing import Union
def value_range(min_value: int, max_value: int):
def decorator(func):
def wrapper(a: Union[int, float], b):
if not min_value <= a <= max_value:
raise ValueError(f"Invalid value for 'a'. It should be between {min_value} and {max_value}.")
return func(a, b)
return wrapper
return decorator
@value_range(1, 3)
def f(a: int, b):
#rest of your functions
pass