04-Working-With-Libraries.md

Using Python Libraries

Index

• Modularization of python program

• Using Python Libraries

  • Using Module

    • Import statement
    • Import with renaming
    • python from import statement
    • import all names

  • Using Package

  • Using Library

  • Using Framwork

Modularization of python program

• Framework = Multiple Libraries

• Library = Multiple Package

• Package = Multiple Modules

• Module = Multiple Functions/Class

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Using Python Libraries

Following terms must be clear while developing any python project/program.

1. Module
2. Package
3. Library
4. Framework

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Using Module

It is a file which contains python functions / global variables / clases etc.

It is just .py file which has python executable code / statement.

For example: Let’s create a file usermodule.py

def hello_world(user_name):
	return "Hello" + user_name

Now we can import usermodule.py module either in python interpreter another py file.

import usermodule
print(usermodule.hello_message("India"))

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How to import modules in Python? Python module can be accessed in any of following way.

Python Import statement

import math
print("2 to the power 3 is", math.pow(2,3))

Just similar to math ,user defined module can be accessed using import statement

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Import with renaming

import math as mt 
print("2 to the power 3 is", mt.pow(2,3))

You can use as keyword to change the name of the module

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Python From Import statement

from math import pow
print("2 to the power 3 is", pow(2,3))

Note - You don't need to provide the Module's name when import a specific function. That is, you don't need to provide math.pow() but instead, you can use pow() directly

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Import all names

from math import *
print("2 to the power 3 is", pow(2,3))

Similar to importing a specific function, Importing all functions does not requires to specify the module's name

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Using Package

• It is namespace that contains multiple package or modules.
• It is a directory which contains a special file __init__.py.
• Let’s create a directory geometry.
• Now this package contains multiple packages / modules to handle user related requests.

Where,

1. Geometry is the top Package
2. Rectangle is first sub Package
3. Circle is second sub Package

Now we can import it in following way in other .py file

from Geometry.Rectangle import area_rect
from Geometry.Circle import perimeter_circ

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Using Library

It is a collection of various packages. Conceptually, There is no difference between package and python library.In Python, a library is used loosely to describe a collection of the core modules.

standard library of Python language comes bundled with the core Python distribution are collection of exact syntax, token and semantics of the Python language. The python standard library lists down approx more than 200 such core modules that form the core of Python.

Additional libraries refer to those optional components that are commonly included in Python distributions. The Python installers automatically adds the standard library and some additional libraries. The additional library is generally provided as a collection of packages. To use such additional library we have to use packaging tools like easyinstall or pip to install such additional libraries.

Define a function moduletest2() in module2.py file and call this function in mylibcall.py file as a part of library1 library. Now run mylibcall.py file It will call moduletest2() method and display-from module2 message. Please make sure that a blank file with __init__.py is created.

Module2.py

def moduletest2():
    print("From Module 2")

Mylibcall.py

from library1.package1 import module2
print(module2.moduletest2())

Using Framework

Framework is like a collection of various libraries which architects some more component. For e.g. Django which has various in-built libraries like Auth, user, database connector etc.

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