Function Arguments

It is also possible to define functions with a variable number of arguments.

Default Argument Values:

The most useful form is to specify a default value for one or more arguments. This creates a function that can be called with fewer arguments than it is defined to allow.

Example

def welcome(person_name,message="Good Day!"):
    return person_name+" "+message  
print(welcome('person1'))
print(welcome('person2','how are you'))
Output:
person1 Good Day!
person2 how are you

Keyword Arguments:

In keyword arguments, the caller identifies the arguments by the parameter name. In a function call, keyword arguments must follow positional arguments.

Example:

def welcome(person_name,message="Good Day!"):
    return person_name+" "+message  
print(welcome(person_name='person1'))
print(welcome(person_name='person2',message='how are you'))
Output:
person1 Good Day!
person2 how are you

Parameters (Formal parameter) and Arguments (Actual parameter)

Scope of Variables

References

Allen B. Downey, “Think Python: How to Think Like a Computer Scientist‘‘, 2nd edition, Updated for Python 3, Shroff/O‘Reilly Publishers, 2016 (http://greenteapress.com/wp/thinkpython/)
Guido van Rossum and Fred L. Drake Jr, ―An Introduction to Python – Revised and updated for Python 3.2, Network Theory Ltd., 2011.
John V Guttag, ―Introduction to Computation and Programming Using Python‘‘, Revised and expanded Edition, MIT Press , 2013
Robert Sedgewick, Kevin Wayne, Robert Dondero, ―Introduction to Programming in Python: An Inter-disciplinary Approach, Pearson India Education Services Pvt. Ltd., 2016.
Timothy A. Budd, ―Exploring Python‖, Mc-Graw Hill Education (India) Private Ltd.,, 2015. 4. Kenneth A. Lambert, ―Fundamentals of Python: First Programs‖, CENGAGE Learning, 2012.
Charles Dierbach, ―Introduction to Computer Science using Python: A Computational Problem-Solving Focus, Wiley India Edition, 2013.
Paul Gries, Jennifer Campbell and Jason Montojo, ―Practical Programming: An Introduction to Computer Science using Python 3‖, Second edition, Pragmatic Programmers, LLC, 2013.