What is Module

Module is logical organize of reusable Python Code. Module groups the related code for easy to understand and use. As we know almost everything on Python are object, Module is also an object that can be bind and reference. Simply, a module is a file that define  functions, classes and variables. A module can also include runnable code.

I will try to elaborate the concept of  Python Module using some simple and easy to understand examples.

Example:

The Python code for a module named “aname” normally resides in a file named aname.py. Here’s an example of a simple module, calc.py-

# calc.py
def add(a,b):
    return a+b

def sub(a,b):
    return a-b

def mul(a,b):
    return a*b

def div(a,b):
    return a/b

I wrote four functions in the calc.py file. We can easily use or call the functions from same file that is calc.py. But, what if , we want to use or call them from another file? To do so we have to import the file or module to the new file. Let create a new file name main.py.You can use any Python source file as a module by executing an import statement in some other Python source file. The import has the following syntax:

import module

In order to import calc module in main.py we need to write following code at first on it

#main.py
import calc.py

 

now all the global variables, functions, classes and so on inside calc.py are accessible from main.py. We can  use the four functions of calc.py as following

import calc
calc.add()
calc.sub()
calc.mul()
calc.div()

The from…import Statement

Python’s from statement lets you import specific attributes from a module into the current namespace. The from…import has the following syntax −

module_name import attribute1, attribute2....

For example, to import the function add from the module calc, use the following statement −

from calc import add

Now, let we have two variables x,y and want to put the summation of them into z
the code is following

#main.py
from calc import add

x=100
y=200
z=add(x,y)

return z #output 300

we can also access other attributes of module.Suppose, the add the constant PI=3.1415926 into calc.py

#calc.py
def add(a,b):
    return a+b

def sub(a,b):
    return a-b

def mul(a,b):
    return a*b

def div(a,b):
    return a/b

#PI Constant Added
PI=3.1415926

we can access the value of PI as following-

import calc
pi=calc.PI
print pi

The dir( ) Function

The dir() built-in function returns a sorted list of strings containing the names defined by a module.

The list contains the names of all the modules, variables and functions that are defined in a module. Following is a simple example −

import calc
content= dir(calc)
print content

 

output:

['__builtins__', '__doc__', '__file__', '__name__', '__package__',
'add', 'div', 'mul', 'sub']

Module is one of vital concept of Python language that frequently used during any kind of python development. I tried to explain the concept in brief using simple examples.

Thats all for today. In the next post I’ll try to discuss on Python Package and Name space. Till then Bye.