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      Arbitrary Arguments

      Python Tutorial

      This Python tutorial has been written for the beginners to help them understand the basic to advanced concepts of Python Programming Language. After completing this tutorial, you will find yourself at a great level of expertise in Python, from where you can take yourself to the next levels to become a world class Software Engineer.

      Arbitrary Arguments

      You may want to define a function that is able to accept arbitrary or variable number of arguments. Moreover, the arbitrary number of arguments might be positional or keyword arguments.
      • An argument prefixed with a single asterisk * for arbitrary positional arguments.
      • An argument prefixed with two asterisks ** for arbitrary keyword arguments.

      Example

      Given below is an example of arbitrary or variable length positional arguments
      # sum of numbers
      def add(*args):
         s=0
         for x in args:
            s=s+x
         return s
      result = add(10,20,30,40)
      print (result)
      
      result = add(1,2,3)
      print (result)
      The args variable prefixed with "*" stores all the values passed to it. Here, args becomes a tuple. We can run a loop over its items to add the numbers.
      It will produce the following output
      100
      6
      It is also possible to have a function with some required arguments before the sequence of variable number of values.

      Example

      The following example has avg() function. Assume that a student can take any number of tests. First test is mandatory. He can take as many tests as he likes to better his score. The function calculates the average of marks in first test and his maximum score in the rest of tests.
      The function has two arguments, first is the required argument and second to hold any number of values.
      #avg of first test and best of following tests
      def avg(first, *rest):
         second=max(rest)
         return (first+second)/2
         
      result=avg(40,30,50,25)
      print (result)
      Following call to avg() function passes first value to the required argument first, and the remaining values to a tuple named rest. We then find the maximum and use it to calculate the average.
      It will produce the following output
      45.0
      If a variable in the argument list has two asterisks prefixed to it, the function can accept arbitrary number of keyword arguments. The variable becomes a dictionary of keyword:value pairs.

      Example

      The following code is an example of a function with arbitrary keyword arguments. The addr() function has an argument **kwargs which is able to accept any number of address elements like name, city, phno, pin, etc. Inside the function kwargs dictionary of kw:value pairs is traversed using items() method.
      def addr(**kwargs):
         for k,v in kwargs.items():
            print ("{}:{}".format(k,v))
      
      print ("pass two keyword args")
      addr(Name="John", City="Mumbai")
      print ("pass four keyword args")
      
      # pass four keyword args
      addr(Name="Raam", City="Mumbai", ph_no="9123134567", PIN="400001")
      It will produce the following output
      pass two keyword args
      Name:John
      City:Mumbai
      pass four keyword args
      Name:Raam
      City:Mumbai
      ph_no:9123134567
      PIN:400001
      If the function uses mixed types of arguments, the arbitrary keyword arguments should be after positional, keyword and arbitrary positional arguments in the argument list.

      Example

      Imagine a case where science and maths are mandatory subjects, in addition to which student may choose any number of elective subjects.
      The following code defines a percent() function where marks in science and marks are stored in required arguments, and the marks in variable number of elective subjects in **optional argument.
      def percent(math, sci, **optional):
         print ("maths:", math)
         print ("sci:", sci)
         s=math+sci
         for k,v in optional.items():
            print ("{}:{}".format(k,v))
            s=s+v
         return s/(len(optional)+2)
      
      result=percent(math=80, sci=75, Eng=70, Hist=65, Geo=72)
      print ("percentage:", result)
      It will produce the following output
      maths: 80
      sci: 75
      Eng:70
      Hist:65
      Geo:72
      percentage: 72.4

      Practice with Online Editor

      Note: This Python online Editor is a Python interpreter written in Rust, RustPython may not fully support all Python standard libraries and third-party libraries yet.
      Remember to save code(Ctrl + S Or Command + S) before run it.