Tuesday, 5 April 2016

Functions in Python with code examples

Functions in Python:

Function is a block of code that is used to perform single action. Functions are reusable. Python has many built-in functions, in additional to that it allows the user to define their own functions which are called as user defined functions.

Defining a function in python:

Python have simple rules to define a function.
Function blocks begin with the keyword def followed by the function name and parentheses ( ( ) ).
The arguments should be placed within these parentheses. we can also define parameters inside these parentheses.
The first statement of a function can be an optional statement - the documentation string of the function or docstring.
The code block within every function starts with a colon (:) and is indented.
The statement return exits a function, optionally passing back an expression to the caller. A return statement with no arguments is the same as return none.


Syntax of the function declaration:

def Namefthefunction( list of parameters separated by comma):

   "function_docstring"

   function_suite

   return [expression]


Example of the Function:

Let us see the below example which accepts two numers as an arguments and returns another number type as the result
def AddNums(val1, val2):


   val3 = val1+val2

   "This prints a sumbe of the above two numbers"

   print val3

   return val3



Function calling in python:

After defining the function as shown above, that specifies the parameters that are to be included in the function and structures the block of the code
def AddNums(val1, val2):

   val3 = val1+val2

   "This prints a sumbe of the above two numbers"

   print val3

   return val3

#calling the function

Result =AddNums (20, 30)


The output of the above code is
50

Function parameter types python:


There are four types of arguments types available in python

Required Arguments:

Required arguments are the arguments passed to a function in correct positional order. Here, the number of arguments in the function call should match exactly with the function definition.

Keyword Arguments:

Keyword arguments are related to the function calls. When you use keyword arguments in a function call, the caller identifies the arguments by the parameter name.

Default arguments:

A default argument is an argument that assumes a default value if a value is not provided in the function call for that argument.

Variable-Length Arguments:

When we need to process a function for more arguments than you specified while defining the function. This type of arguments are called variable-length arguments and are not named in the function definition, unlike required and default arguments.

AS we know Pthon is strongly typed because every object has a type, every object knows its type, it's impossible to accidentally or deliberately use an object of a type "as if" it was an object of a different type, and all elementary operations on the object are delegated to its type.

This has nothing to do with names. A name in Python doesn't "have a type": if and when a name's defined, the name refers to an object, and the object does have a type



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