Python libraries

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Learning objectives
• Understanding Library
• Importing Modules in Python Program
• Using Standard Library’s functions
• Creating a Python Library

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What is a Library?
• A Library refers to a collection of modules that together
cater to specific types of needs or applications.
• Some Commonly used Python library are:
Library Functions
standard library This library is distributed with Python that contains modules for
various types of functionalities.
NumPy library This library provides some advance math functionalities along with
tools to create and manipulate numeric arrays.
SciPy library This is another useful library that offers algorithmic and
mathematical tools for scientific calculations.
tkinter library This library provides traditional Python user interface toolkit and
helps you to create user friendly GUI interface for different types
of applications.
Malplotlib library This library offers many functions and tools to produce quality
output in variety of formats such as plots, charts, graphs

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Python standard library
• Some commonly used modules of Python standard library
are:
Library Functions
math module Provides mathematical functions to support different
types of calculations.
cmath module provides mathematical functions for complex numbers
random module provides functions for generating pseudo-random
numbers
statistics module provides mathematical statistics functions
Urllib module provides URL handling functions so that you can access
websites from within your program

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What is a Module?
• Python module is a file(.py file) containing variables, class
definitions, statements and functions related to a particular task.
• A Module, in general:
 Is independent grouping of code and data
 Can be re-used in other programs.
 Can depend on other modules

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Structure of a Python Module
• A Python module can contain much more than just functions.
• A Python module is a normal Python file (.py file) containing one or
more of the following objects related to a particular task:
• So, we can say that the module ‘ABC' means it is file ‘ABC.py’
Structure Task
docstrings triple quoted comments; useful for documentation purposes.
variables and
constants
labels for data
classes templates/blueprint to create objects of a certain kind
objects instances of classes. In general, objects are representation
of some real or abstract entity
statements Instructions for processing
functions named group of instructions

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Importing Modules
• Python module files have an extension .py
• These modules can be imported in the following ways:
 import statement
- to import entire module
 from statement
- to import selected object
 from * statement
- import all names from the module

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IMPORTING MODULES- import
• import statement is used to include the modules in other
programs.
 syntax : import <filename>
 example: import math
• more than one module can be inserted in a python program
 syntax : import <filename> ,<filename>,<filename>……
 example: import math,os
• using import statement one can view all the functions and
other attributes of a particular module
 example:
import math
dir(math)

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IMPORTING MODULES- from
• importing module can be done using from statement
specific attributes can be included in other programs.
• syntax :
• from <filename> import function name
• example:
• from math import math.sqrt

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IMPORTING MODULES- from*
• from* statement can be used to import all names from the
module in to the current calling name space.
• syntax :
from <filename> import *
• example:
from math import *
math.sqrt(4)
• we can access any function by using dot notation.

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NAMESPACES
When we import modules in a particular program these modules will
become part of that program and are called as namespace.
Python implements namespaces in the form of dictionaries. It maintains a
name to object mapping.
There are three types of namespaces
1) Global
2) Local
3) Built in
Namespaces

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MODULE ALIASING
• One can create an alias while importing module in a program
• Syntax:
import <filename> as <alias name>
• Example:
import math as m
m.sqrt(4)
• Like module aliasing members are also aliased
• syntax:
import <filename> as <alias name>,member as alias name
• Example:
import test as t, add as sum
test.py is module file and is referred to as t and add is the function,
it is referred to as sum.

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PACKAGE/LIBRARY
• Python packages are the collection of related modules.
You can import a package or create your own.
• Python package is a simply directory of python modules
• Steps to create and import a package
1. create a directory named ‘Gemetry’
2. add modules area.py and volume.py
3. create a file __init__.py in directory ‘Geometry’. The __init__.py
files are required to make python treat the directory as containing
package

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PACKAGE/LIBRARY
• What is __init__.py file?
• __init__.py is simply a file used to consider directories on the disk as
package of python.
• It is basically used to initilize the python package
• Python searches module in the following manner
• 1) Searches in current directory
• 2) If the module is not found then searches each directory in the shell variable
PYTHONPATH
• 3) If all else fails, python checks the default path which is the installation location
of the python

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pip
• What is pip?
• pip is a package-management system used to install and manage
software packages written in Python.
• To check pip version run, pip --version at dos prompt

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• We learned about the Python Library .
• Types of Libraries
• Modules in Python
• Packages in Python.
• We also looked at the creating PACKAGE/LIBRARY.
Thank you
Conclusion!

Python libraries

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