collection

Modules

• A module is simply a Python file, where classes, functions and variables are defined.
• These modules can be imported in our project whenever required.
• There are 2 types of modules:
  • Built-in Modules
  • User-define Modules

Built-in Modules

1. math :for mathematical functions.
2. threading : for multithreaded applications.
3. collections : for additional collections classes.
4. os : operating system related functions.
5. re : for text processing
6. random : for random number generation
7. pickle : is used for serializing and de-serializing Python objects.
8. nltk : natural language processing.
9. datetime : is used to perform operations on date and time data.
10. tkinter : for GUI interface.
11. sockets : for network programming.

Importing modules

• It is used to import a module.

import <module-name1, module-name2… >

• It is used to import particular attribute from a module.

from <modulename> import <attributename>,..

• we can create an alias when we import a module.

import <modulename> as <aliasname>

User-defined Modules

• Create a file having same name as modulename.
• In that file we can define any type of components such as functions,variables, classes, objects etc.

class Rectangle:
  def setdimension(self,x,y):
    self.length=x
    self.breadth=y
  def area(self):
    a=self.length*self.breadth
    print("Area is ",a)

class Circle:
  def setradius(this,n):
    this.r=n
  def area(this):
    a=3.14*this.r**2
    print("Area is ",a)

def display(n):
  for i in range(1,n+1):
    print(i)

import mylib
a=mylib.Circle()
b=mylib.Rectangle()
a.setradius(5)
b.setdimension(5,10)
a.area()
b.area()
mylib.display(5)

Area is 78.5
Area is 50
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class Rectangle:
  def setdimension(self,x,y):
    self.length=x
    self.breadth=y
  def area(self):
    a=self.length*self.breadth
    print("Area is ",a)

class Circle:
  def setradius(this,n):
    this.r=n
  def area(this):
    a=3.14*this.r**2
    print("Area is ",a)

def display(n):
 for i in range(1,n+1):
 print(i)

from mylib import Circle

a=Circle()
a.setradius(5)
a.area()

Area is 78.5

class Rectangle:
  def setdimension(self,x,y):
    self.length=x
    self.breadth=y
  def area(self):
    a=self.length*self.breadth
    print("Area is ",a)

class Circle:
  def setradius(this,n):
    this.r=n
  def area(this):
    a=3.14*this.r**2
    print("Area is ",a)

def display(n):
 for i in range(1,n+1):
 print(i)

import mylib as lib
a=lib.Circle()
a.setradius(5)
a.area()

from mylib import 
Rectangle as rect

a=rect()
a.setdimension(5,10)
a.area()

Area is 78.5
Area is 50

PYTHONPATH environment variable

• PYTHONPATH is an environment variable which you can set to add additional directories where python will look for modules and packages.
• For windows system
  • Set environment variables in system.properties
  • PYTHONPATH = directoryName