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Python Concepts: args & kwargs

Concept No1: *args and **Kwargs:


Args and kwargs allow you to pass multiple arguments in the case of args, or keyword in the case of kwarg.

Normally, you can define the function with previous known number of arguments, but what if you want to have it work for unknown number of arguments which will be determine during the runtime. Here comes the functionality of *args.


Lets see a normal function:

def sum(no1, no2):
  return no1 + no2

Now, a function with a list of predetermined number of values:


def sum(list_of_no):
  result = 0
  for x in list_of_no:
    result +=x
  return result

list_of_no= [2,5,6]
sum(list_of_no)

Despite that this solution allows the user to apply the function for multiple variables, still though it requires the no of variables to be determined previously. Thus, *args come to place.

When passing *args the function will accept any number of variables without predetermination of this number, and then will loop through them successfully.

It does not need to be args, it could be any other name, but it needs to have the asterisk as it works to unpack the tuple of variables into single iterable object called args. Here we are not passing a list, instead we’re passing three different positional arguments as a tuble, which is immutable object that cannot be modified.


def sum(*args):
    result = 0
    # Iterating over the Python args tuple
    for x in args:
        result += x
    return result

sum(2,5,6)

or, simply:


def sum(*variables):
    result = 0
    # Iterating over the Python variables tuple
    for x in variables:
        result += x
    return result

sum(2,5,6)

Now, what about **kwargs?


It works just as *args, but instead it accepts any number of keywords or names.

Thus, *args are positional arguments which are declared using the name only, while **kwargs are keyword arguments which are declared using a name and a value; it is a dictionary.

def keyarguments(a, b, **kwargs):
  print(a)
  print(b)
  print(kwargs)

keyarguments(5,6, third_no = 7, forth_no = 8)

the result will be:

5
6
{'third_no': 7, 'forth_no': 8}

It turned the last two passed arguments in keyarguments function into a name value paired as a dictionary.


Note: when passing **kwargs, it should not be before the normal numbers, or else it will raise a syntax error.


Lets try to iterate over **kwargs as in dictionaries:

def show_data(**kwargs):
    print("\nType of argument:",type(kwargs))

    for key, value in kwargs.items():
        print("{} is {}".format(key,value))

show_data(Name= "sana", Program= "data science", Platform= "Data Insight")

The result is:

Type of argument: <class 'dict'>
Name is sana
Program is data science
Platform is Data Insight

We can see clearly that type of **kwargs is dictionary.


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