Python Functions Arguments

In python, there are following four types of formal arguments :

  1. Required arguments
  2. Keyword arguments
  3. Default arguments
  4. Variable number of arguments

Required arguments :

  • Arguments follow the positional order.

  • The number of arguments and order of arguments in the function call must be the same as that in the function definition.

Example :

# function definition
def myfun(arg1):
    print("Value of arg1 ",arg1)

# function invocation with required argument

TypeError: myfun() missing 1 required positional argument: 'arg1'

As you can see int the above program, we are getting the error because the number of arguments is not matching at the time of function call.

Keyword Arguments :

  • When used in function call, calling function identifies the argument by parameter name.

  • Allow us to change the the positional order of arguments.

  • Python interpreter uses the keyword provided to match the values with parameters.

Example :

# function definition
def myfun(name, roll_num):
    print("Name of student ", name)
    print("Roll Number of student ", roll_num)

# function invocation with keyword argument

myfun(name='Daneyel', roll_num=1001)
myfun(roll_num=1001,name='Daneyel')  # change the order

Default Arguments :

  • At the time of function definition, we set a value for the arguments that serve as default arguments.

  • At the time of function call, if we do not provide the value for that argument, then the default value will be used.

In function definition, non-default parameter must not follow default parameter.


# function definition
def myfun(product, tax_rate=4, offer):  #ERROR, non-default parameter follows default parameter
def myfun1(product, tax_rate=4, offer=5):

Program to understand the use of default argument

# function definition
def myfun(product, tax_rate=4):
    print("Product ", product, " with tax ",tax_rate)
# function invocation with keyword argument

myfun(product='Maggi')  # default will use
# OR
myfun(product='Tomato-Ketchup', tax_rate=6)
Product  Maggi  with tax  4  # default used
Product  Tomato-Ketchup  with tax  6

Next chapter is Python Functions Arguments


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