How can i set specifiques arguments to python's function like C

Question

please how can I specify the return values of a function and types of arguments it required , like in C we declare a prototype function like this and type it requires :

int *atoi(char *str)

Answer 1

You can use this for both arguments and variables. But the problem is the this type can be changed at any time when assigning.

a:int = 4

but this also will work without raising error

a:int = "this is string"

and lets get function arguments

def func(arg1:int , arg2:str = "hello"): -> str
    #do something

The above function will take an integer as first argument , string as the second one and will output a string.

But there is no contrains like C or java. Such like arguments must be in the specified data type only. The same is for the output data type also.

Answer 2

Unfortunately, in python there's no definitive ways of constraining. I.e. you can write code like this:

def func(a:int, b:str):
    print(type(a))
    print(type(b))

func("Hello!", 31)
# >>> <class 'str'>
# >>> <class 'int'>

If you want to set constraints on code, I would suggest setting up a try/except clause which tries to convert to the correct type, and raises an error if it does not work. Like so:

def func(a:int, b:str):
    try:
        a = int(a)
    except ValueError:
        raise ValueError(f"Input {a =} not understood as integer. ")

    try:
        b = str(b)
    except ValueError:
        raise ValueError(f"Input {b =} not understood as string. ")

# func("Hello!", 31) # raises value errors.
func(31, "Hello!") # passes. With variables cast to right type.