Defining functions

Key 1: How to define functions.

Functions are used to group a set of instructions and logic that performs a specific task. So, we should make functions perform one specific task and choose a name that gives us a hint about that. If a function is important and performs complex stuff, we should always add docstrings to this function so that it is easy for us to later visit and modify this function.

While defining a function, we can define the following:

1. Positional arguments (simply pass the object according to position), which are as follows:

   >>> def foo(a,b):
   ...   print(a,b)
   ... 
   >>> foo(1,2)
   1 2

2. Default arguments (if value is not passed, the default is used), which are as follows:

   >>> def foo(a,b=3):
   ...    print(a,b)
   ... 
   >>> foo(3)  
   3 3
   >>> foo(3,4)
   3 4

3. Keyword only arguments (must be passed as a positional or as a keyword argument), which are as follows:

   >>> def  foo(a,*,b):
   ...   print(a,b)
   ... 
   >>> foo(2...