12/12/2023 0 Comments Tuple unpacking python![]() Use Python *arg arguments for a function that accepts a variable number of arguments.When you precede the argument a with the operator *, Python unpacks the tuple and assigns its elements to x and y parameters. To fix this, you need to prefix the tuple a with the operator * like this: def point(x, y): If you pass a tuple to the point function, you’ll get an error: a = (0, 0)Įrror: TypeError: point() missing 1 required positional argument: 'y' Code language: JavaScript ( javascript ) Return f '()' Code language: JavaScript ( javascript ) The following point function accepts two arguments and returns a string representation of a point with x-coordinate and y-coordinate: def point(x, y): In this example, Python assigns 10 to x, 20 to y, (30,40) to args, and 50 to z. ![]() To fix it, you need to use a keyword argument after the *args argument as follows: def add(x, y, *args, z): The following example results in an error because it uses a positional argument after the *arg argument: def add(x, y, *args, z):Įrror: TypeError: add() missing 1 required keyword-only argument: 'z' Code language: JavaScript ( javascript ) If you use the *args argument, you cannot add more positional arguments. Output: 6 Code language: Python ( python ) Python *args argument exhausts positional arguments Print(total) Code language: Python ( python ) The following shows how to add all numbers of the args tuple in the add() function: def add (*args): To access each element of the args argument, you use the square bracket notation with an index: def add (*args):Īlso, you an use a for loop to iterate over the elements of the tuple. Now, the args has three numbers 1, 2, and 3. Output: ( 1, 2, 3) Code language: Python ( python ) The following passes three arguments to the add() function: def add (*args):Īdd( 1, 2, 3) Code language: Python ( python ) Since we didn’t pass any argument to the add() function, the output shows an empty tuple. The following shows the type of the args argument and its contents: def add (*args): Output: () Code language: Python ( python ) Let’s take a look at the following example: def add (*args): However, by convention, Python uses the *args for a variadic parameter. For example, you can use any meaningful names like *numbers, *strings, *lists, etc. ![]() Note that you don’t need to name args for a variadic parameter. Functions that have variadic parameters are called variadic functions. In Python, the parameters like *args are called variadic parameters. ![]() And you can pass zero, one, or more arguments to the *args parameter. When a function has a parameter preceded by an asterisk ( *), it can accept a variable number of arguments. Introduction to the Python *args parameter It’s like tuple unpacking except that the args is a tuple, not a list. When passing the positional arguments 10, 20, 30, and 40 to the function, Python assigns 10 to x, 20 to y, and a tuple (30, 40) to args. The *args is a special argument preceded by a star ( *). The add function accepts three parameters x, y, and *args. Python uses the same concept for the function arguments. Similarly, the following assigns 10 to x, 20 to y, and the list to z: x, y, *z = 10, 20, 30, 40 print(x) In this example, Python passed 10 to x and 20 to y. It’s similar to passing two arguments to a function: def add(x, y): The following unpacks a tuple into two variables: x, y = 10, 20 Summary: in this tutorial, you’ll learn about the Python *args parameters and how to use them for defining variadic functions.
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