12/30/2023 0 Comments Python unpacking argumentsI’d say what *t assigns to has nothing to do with the function definition of f, but only the surrounding arguments in the calling code. ![]() So, *t will assign to the positional arguments of f The reasoning that because x is a required argument by f definition,….There is one point i disagree with in your first answer: Note that the error changed it’s description of “argument x” to “keyword argument x” just based on a different way of calling ![]() def f (x, y, z) :į(2, **d) # TypeError: f() got multiple values for argument 'x'į(x=2, **d) # TypeError: f() got multiple values for keyword argument 'x' Here is another example to show the unreliability of associating the words positional/keyword argument with the function definition side. Because it confuses the positional argument in function definition with position argument in calling code. I see this as confusing term definition in error message. TypeError: f() missing 1 required positional argument: 'z' I know TypeErrors call the function definition side position/keyword arguments too. Compound statements - Python 3.12.0 documentation treat them as “parameters” and “parameters with default values”. Expressions - Python 3.12.0 documentation, the terms positional argument and keyword argument are applicable to the calling side, can’t find mention of them on the function definition side. Your first answer mixed these two, making references to both the function definition, and the code calling the function.Īccording to 6. Is there actually such a distinction between positional/keyword argument when talking about the function definition? I thought that was a distinction applied to the calling line, not the function definition/function being called. Let me know if you need further help or see any me try to repeat my question bolded at the important parts and clarify exact what i am concerned about. Important to note that positional argument comes first before any other types of arguments otherwise, you have a Synta圎rror: positional argument follows keyword argument. x has to be declared first if you going to use a keyword argument, but it will error out (see error case 1).Įxample using tuple/dictionary unpacking when calling function f: t = (5, 15)į(2, *t) # using argument unpacking, returns į(2, *(3, 4)) # using tuple unpacking, returns į(2, **) # using dictionary unpacking, returns However, the positional order is incorrect. And, second element of positional argument of f will be assigned to y. So, the first element of positional argument of f will be assigned to x. You see 4, 5 are the positional arguments. ![]() Lastly, a third error occurred due to missing required parameter of z.Įrror case 2: f(z=2, 4, 5) actually points to f(z=2, x=4, y=5). Hence, the first error occurred due to positional argument needs to be first before keyword argument.Ī second error occurred due to multiple values of x being assigned. And, second element of positional argument of f will be assigned to y.Īnd, we know that x=1 is a keyword argument because of the usage of = assignment operator. You see 2, 3 are the positional arguments. These are the only valid cases to use a keyword argument in function f because it satisfy the rule - positional arguments comes first before keyword arguments.Īnd, all three required arguments are met. By using argument names, it is possible to switch the order of arguments.Įxample using default positioning when calling function f: f(1, 2, 3) # returns Įxample using argument names when calling function f: f(1, 2, z=4) # returns However, it is possible to use argument names when calling the functions. The function call to f requires three arguments. They do not have any default value.įor function f, x has a positional order of 1. Positional parameter are mandatory and have no default values but has natural positional order. The above code will give the following error: Synta圎rror: non-default argument follows default argument Y, z= *t # Assigned by position, second and third position in the argument list x = 2 # Assigned by position, first position in the argument list Here, all arguments are being assigned by position since there isn’t any keyword-only arguments. ![]() As a result, there’s a error for multiple values of x.Īnd, you might have an error of missing argument for z. Hence, we have: x = 2 # Assigned by keyword argument So, *t will assign to the positional arguments of f. However by the function f definition, x is a required argument, which is also a positional argument. Here, x=2 is defined as keyword-only argument (keyword-only argument syntax: variable=some_value). Given the function definition as describe above: def f (x, y, z) : Putting the default arg after *args in Python 3 makes it a “keyword-only” argument that can only be specified by name, not by position.
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