Network Programming

• Network applications are everywhere. 

• Any time you browse the Web, send an email message, or pop up an X window, you are using a network application.

• Python provides two levels of access to network services.

•  At a low level, you can access the basic socket support in the underlying operating system,which allows you to implement clients and servers for both connection-oriented and connection-less protocols.
• Python also has libraries that provide higher-level access to specific application-level network protocols, such as FTP, HTTP, and so on.

• understanding on most famous concept in Networking - Socket Programming.

What is Socket ?

• Sockets are the endpoints of a bidirectional communications channel. 

• Sockets may communicate within a process, between processes on the same machine, or between processes on different continents.

• Sockets may be implemented over a number of different channel types: Unix domain sockets, TCP, UDP, and so on. 

Client:

import socket               

# Import socket module

s = socket.socket( )         

# Create a socket object

host = socket.gethostname( ) 

# Get local machine name

port = 12345                

# Reserve a port for your service

s.connect((host, port))

print s.recv(1024)

s.close  

Client example2:

 import socket

clientsocket=socket.socket(socket.AF_INET, socket.SOCK_STREAM)

clientsocket.connect(('localhost', 8089))

clientsocket.send('hello')

Client example3:

import socket

import sys

# Create a TCP/IP socket

sock=socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# Connect the socket to the port where the server is listening

server_address = ('localhost', 9999)

print >>sys.stderr, 'connecting to %s port %s' % server_address

sock.connect(server_address)

try:

    

    # Send data

    message = 'This is the message.  It will be repeated.'

    print >>sys.stderr, 'sending "%s"' % message

    sock.sendall(message)

    # Look for the response

    amount_received = 0

    amount_expected = len(message)

    

    while amount_received < amount_expected:

        data = sock.recv(16)

        amount_received += len(data)

        print >>sys.stderr, 'received "%s"' % data

finally:

    print >>sys.stderr, 'closing socket'

    sock.close( )

Server :

import socket               

# Import socket module

s = socket.socket( )         

# Create a socket object

host = socket.gethostname( ) 

# Get local machine name

port = 12345                

# Reserve a port for your service.

s.bind((host, port))        

# Bind to the port

s.listen(5)                 

# Now wait for client connection.

while True:

   c, addr = s.accept()     

# Establish connection with client.

   print 'Got connection from', addr

   c.send('Thank you for connecting')

   c.close()                

# Close the connection

Server example2:

import socket

serversocket=socket.socket(socket.AF_INET, socket.SOCK_STREAM)

serversocket.bind(('localhost', 8089))

serversocket.listen(5) 

# become a server socket, maximum 5 connections

while True:

    connection, address = serversocket.accept()

    buf = connection.recv(64)

    if len(buf) > 0:

        print buf

        break

Server Example3:

import socket

import sys

# Create a TCP/IP socket

sock=socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# Bind the socket to the port

server_address = ('localhost', 9999)

print >>sys.stderr, 'starting up on %s port %s' % server_address

sock.bind(server_address)

# Listen for incoming connections

sock.listen(1)

while True:

    # Wait for a connection

    print >>sys.stderr, 'waiting for a connection'

    connection, client_address = sock.accept()

    try:

        print >>sys.stderr, 'connection from', client_address

        # Receive the data in small chunks and retransmit it

        while True:

            data = connection.recv(16)

            print >>sys.stderr, 'received "%s"' % data

            if data:

                print >>sys.stderr, 'sending data back to the client'

                connection.sendall(data)

            else:

                print >>sys.stderr, 'no more data from', client_address

                break

            

    finally:

        # Clean up the connection

        connection.close( )

Connecting to server:

example:

import socket
ip = socket.gethostbyname('www.google.com')
print ip

example:

import socket 

import sys 

try:

    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

    print "Socket successfully created"

except socket.error as err:

    print "socket creation failed with error %s" %(err)

# default port for socket

port = 80

try:

    host_ip = socket.gethostbyname('www.google.com')

except socket.gaierror:

    # this means could not resolve the host

    print "there was an error resolving the host"

    sys.exit()

# connecting to the server

s.connect((host_ip,port))

print "the socket has successfully connected to google \

on port == %s" %(host_ip)

Server:

# first of all import the socket library
import socket              

# next create a socket object
s = socket.socket()        
print "Socket successfully created"

# reserve a port on your computer in our
# case it is 12345 but it can be anything
port = 12345              

# Next bind to the port
# we have not typed any ip in the ip field
# instead we have inputted an empty string
# this makes the server listen to requests
# coming from other computers on the network
s.bind(('', port))      
print "socket binded to %s" %(port)

# put the socket into listening mode
s.listen(5)    
print "socket is listening"          

# a forever loop until we interrupt it or
# an error occurs
while True:
   # Establish connection with client.
   c, addr = s.accept()    
   print 'Got connection from', addr

   # send a thank you message to the client.
   c.send('Thank you for connecting')
   # Close the connection with the client
   c.close()              

Client:

# Import socket module
import socket              

# Create a socket object
s = socket.socket()        

# Define the port on which you want to connect
port = 12345              

# connect to the server on local computer
s.connect(('127.0.0.1', port))

# receive data from the server
print s.recv(1024)
# close the connection
s.close()                     

         

Hard copy and Shallow copy and Deep copy

>>> import copy

>>> par_list=[1,2,3]

>>> c1_list=par_list

>>> c2_list=copy.copy(par_list)

>>> c3_list=copy.deepcopy(par_list)

>>> par_list==c1_list
True

>>> par_list is c1_list
True

>>> par_list == c2_list
True

>>> par_list is c2_list
False

>>> par_list ==c3_list
True

>>> par_list is c3_list
False

>>> par_list
[1, 2, 3]

>>> par_list[1]='siva'

>>> par_list
[1, 'siva', 3]

>>> c1_list
[1, 'siva', 3]

>>> c2_list
[1, 2, 3]

>>> c3_list
[1, 2, 3]

>>> c1_list[1]=3+4j

>>> c1_list
[1, (3+4j), 3]

>>> par_list
[1, (3+4j), 3]

>>> c2_list
[1, 2, 3]

>>> c3_list
[1, 2, 3]

>>> c2_list[1]=2.3

>>> c2_list
[1, 2.3, 3]

>>> par_list
[1, (3+4j), 3]

>>> c1_list
[1, (3+4j), 3]

>>> c3_list
[1, 2, 3]

>>> c3_list[1]='krishna'

>>> c3_list
[1, 'krishna', 3]

>>> par_list
[1, (3+4j), 3]

>>> c1_list
[1, (3+4j), 3]

>>> c2_list
[1, 2.3, 3]

#multi dimensional list

>>> p_list=[1,2,3,[4,5,[6,7]]]

>>> ch1_list=p_list

>>> ch1_list
[1, 2, 3, [4, 5, [6, 7]]]

>>> ch2_list=copy.copy(p_list)

>>> ch2_list
[1, 2, 3, [4, 5, [6, 7]]]

>>> ch3_list=copy.deepcopy(p_list)

>>> ch3_list
[1, 2, 3, [4, 5, [6, 7]]]

>>> p_list==ch1_list==ch2_list==ch3_list
True

>>> p_list is ch1_list,p_list is ch2_list,p_list is ch3_list
(True, False, False)


>>> p_list[3][2][1]
7

>>> p_list[3][2][1]='siva'

>>> p_list
[1, 2, 3, [4, 5, [6, 'siva']]]

>>> ch1_list
[1, 2, 3, [4, 5, [6, 'siva']]]

>>> ch2_list
[1, 2, 3, [4, 5, [6, 'siva']]]

>>> ch3_list
[1, 2, 3, [4, 5, [6, 7]]]
>>> 

Python2.x v/s Python3.x

• print statement vs print( ) function

• raw_input( ) => input( )

• xrange( ) vs range( )

• Integer division

Data Analysis and Reporting

Data Analysis:

install pandas module

pip install pandas

after installing importing the pandas module

import pandas

Help on pandas:

import pandas
help(pandas.DataFrame)

Example:

from pandas import DataFrame, read_csv
import pandas as pd
import matplotlib.pyplot as plt
names = ['Bob','Jessica','Mary','John','Mel']
births = [968, 155, 77, 578, 973]
BabyDataSet = list(zip(names,births))
print(BabyDataSet)
df = pd.DataFrame(data = BabyDataSet, columns=['Names', 'Births'])
print(df)
df.to_csv('births1880.csv',index=False,header=False)
df = pd.read_csv('births1880.csv')
print(df)
df = pd.read_csv('births1880.csv', header=None)
print(df)
df = pd.read_csv('births1880.csv', names=['Names','Births'])
print(df)
Sorted = df.sort_values(['Births'], ascending=False)
print(Sorted.head(1))
print(df['Births'].max())
print(df['Names'])

print(df['Births'])

Example2:

import pandas as pd
from numpy import random
import matplotlib.pyplot as plt
import os
import sys #only needed to determine Python version number
import matplotlib #only needed to determine Matplotlib version number
names = ['Bob','Jessica','Mary','John','Mel']
random.seed(500)
random_names = [names[random.randint(low=0,high=len(names))] for i in range(1000)]
# Print first 10 records
print(random_names[:10])
births = [random.randint(low=0,high=1000) for i in range(1000)]
print(births[:10])
BabyDataSet = list(zip(random_names,births))
print(BabyDataSet[:10])
df = pd.DataFrame(data = BabyDataSet, columns=['Names', 'Births'])
print(df[:10])
df.to_csv('births1880.txt',index=False,header=False)
df = pd.read_csv('births1880.txt')
print(df.info())
df = pd.read_csv('births1880.txt', header=None)
print(df.info())
print(df.tail())
df = pd.read_csv('births1880.txt', names=['Names','Births'])
print(df.head(5))
print(df['Names'].unique())
for x in df['Names'].unique():
    print(x)
print(df['Names'].describe())
name = df.groupby('Names')

# Apply the sum function to the groupby object
df = name.sum()
print(df)
Sorted = df.sort_values(['Births'], ascending=False)

print(Sorted.head(1))

Example3:

import pandas as pd
# Our small data set
d = {'one':[1,1,1,1,1],
     'two':[2,2,2,2,2],
     'letter':['a','a','b','b','c']}
# Create dataframe
df = pd.DataFrame(d)
print(df)
one = df.groupby('letter')
# Apply sum function
print(one.sum())
letterone = df.groupby(['letter','one']).sum()

print(letterone)

Example4:

import pandas as pd
import sys
# Create a dataframe with dates as your index
States = ['NY', 'NY', 'NY', 'NY', 'FL', 'FL', 'GA', 'GA', 'FL', 'FL'] 
data = [1.0, 2, 3, 4, 5, 6, 7, 8, 9, 10]
idx = pd.date_range('1/1/2012', periods=10, freq='MS')
df1 = pd.DataFrame(data, index=idx, columns=['Revenue'])
df1['State'] = States

# Create a second dataframe
data2 = [10.0, 10.0, 9, 9, 8, 8, 7, 7, 6, 6]
idx2 = pd.date_range('1/1/2013', periods=10, freq='MS')
df2 = pd.DataFrame(data2, index=idx2, columns=['Revenue'])
df2['State'] = States
# Combine dataframes
df = pd.concat([df1,df2])
print(df)
newdf = df.copy()

newdf['x-Mean'] = abs(newdf['Revenue'] - newdf['Revenue'].mean())
newdf['1.96*std'] = 1.96*newdf['Revenue'].std()  
newdf['Outlier'] = abs(newdf['Revenue'] - newdf['Revenue'].mean()) > 1.96*newdf['Revenue'].std()
print(newdf)



Data science/data reporting:

import matplotlib.pyplot as plt
plt.plot([1,2,3],[5,7,4])
plt.show( )

Example2:

import matplotlib.pyplot as plt

x = [1,2,3]
y = [5,7,4]

x2 = [1,2,3]
y2 = [10,14,12]

plt.plot(x, y, label='First Line')
plt.plot(x2, y2, label='Second Line')
plt.xlabel('Plot Number')
plt.ylabel('Important var')
plt.title('Interesting Graph\n Check it out')
plt.legend( )
plt.show( )



Example3:

import matplotlib.pyplot as plt
plt.bar([1,3,5,7,9],[5,2,7,8,2], label="Example one")

plt.bar([2,4,6,8,10],[8,6,2,5,6], label="Example two", color='g')
plt.legend()
plt.xlabel('bar number')
plt.ylabel('bar height')

plt.title('Epic Graph\n Another Line! Whoa')

plt.show( )

Example4:

import matplotlib.pyplot as plt

population_ages = [22,55,62,45,21,22,34,42,42,4,99,102,110,120,121,122,130,111,115,112,80,75,65,54,44,43,42,48]

bins = [0,10,20,30,40,50,60,70,80,90,100,110,120,130]

plt.hist(population_ages, bins, histtype='bar', rwidth=0.8)

plt.xlabel('x')

plt.ylabel('y')

plt.title('Interesting Graph\nCheck it out')

plt.legend( )

plt.show( )

Example5:

import matplotlib.pyplot as plt

x = [1,2,3,4,5,6,7,8]

y = [5,2,4,2,1,4,5,2]

plt.scatter(x,y, label='skitscat', color='k', s=25, marker="o")

plt.xlabel('x')

plt.ylabel('y')

plt.title('Interesting Graph\nCheck it out')

plt.legend( )

plt.show( )

Example6:

import matplotlib.pyplot as plt

days = [1,2,3,4,5]

sleeping = [7,8,6,11,7]
eating =   [2,3,4,3,2]
working =  [7,8,7,2,2]
playing =  [8,5,7,8,13]
plt.stackplot(days, sleeping,eating,working,playing, colors=['m','c','r','k'])

plt.xlabel('x')
plt.ylabel('y')
plt.title('Interesting Graph\nCheck it out')

plt.show( )

example:

import matplotlib.pyplot as plt

days = [1,2,3,4,5]

sleeping = [7,8,6,11,7]

eating =   [2,3,4,3,2]

working =  [7,8,7,2,2]

playing =  [8,5,7,8,13]

plt.plot([],[],color='m', label='Sleeping', linewidth=5)

plt.plot([],[],color='c', label='Eating', linewidth=5)

plt.plot([],[],color='r', label='Working', linewidth=5)

plt.plot([],[],color='k', label='Playing', linewidth=5)

plt.stackplot(days, sleeping,eating,working,playing, colors=['m','c','r','k'])

plt.xlabel('x')

plt.ylabel('y')

plt.title('Interesting Graph\nCheck it out')

plt.legend( )

plt.show( )

example8:

import matplotlib.pyplot as plt

slices = [7,2,2,13]

activities = ['sleeping','eating','working','playing']

cols = ['c','m','r','b']

plt.pie(slices,

        labels=activities,

        colors=cols,

        startangle=90,

        shadow= True,

        explode=(0,0.1,0,0),

        autopct='%1.1f%%')

plt.title('Interesting Graph\n Check it out')

plt.show( )

sorting techniques

Bubble sort:


def bubbleSort(alist):
    for passnum in range(len(alist)-1,0,-1):
        for i in range(passnum):
            if alist[i]>alist[i+1]:
                temp = alist[i]
                alist[i] = alist[i+1]
                alist[i+1] = temp

alist = [54,26,93,17,77,31,44,55,20]
bubbleSort(alist)
print(alist)

insertion sort:

def insertionSort(alist):
   for index in range(1,len(alist)):

     currentvalue = alist[index]
     position = index

     while position>0 and alist[position-1]>currentvalue:
         alist[position]=alist[position-1]
         position = position-1

     alist[position]=currentvalue

alist = [54,26,93,17,77,31,44,55,20]
insertionSort(alist)
print(alist)

merge sort:

def mergeSort(alist):

    print("Splitting ",alist)

    if len(alist)>1:

        mid = len(alist)//2

        lefthalf = alist[:mid]

        righthalf = alist[mid:]

        mergeSort(lefthalf)

        mergeSort(righthalf)

        i=0

        j=0

        k=0

        while i < len(lefthalf) and j < len(righthalf):

            if lefthalf[i] < righthalf[j]:

                alist[k]=lefthalf[i]

                i=i+1

            else:

                alist[k]=righthalf[j]

                j=j+1

            k=k+1

        while i < len(lefthalf):

            alist[k]=lefthalf[i]

            i=i+1

            k=k+1

        while j < len(righthalf):

            alist[k]=righthalf[j]

            j=j+1

            k=k+1

    print("Merging ",alist)

alist = [54,26,93,17,77,31,44,55,20]

mergeSort(alist)

print(alist)

Quick sort:

def quickSort(alist):

   quickSortHelper(alist,0,len(alist)-1)

def quickSortHelper(alist,first,last):

   if first<last:

       splitpoint = partition(alist,first,last)

       quickSortHelper(alist,first,splitpoint-1)

       quickSortHelper(alist,splitpoint+1,last)

def partition(alist,first,last):

   pivotvalue = alist[first]

   leftmark = first+1

   rightmark = last

   done = False

   while not done:

       while leftmark <= rightmark and alist[leftmark] <= pivotvalue:

           leftmark = leftmark + 1

       while alist[rightmark] >= pivotvalue and rightmark >= leftmark:

           rightmark = rightmark -1

       if rightmark < leftmark:

           done = True

       else:

           temp = alist[leftmark]

           alist[leftmark] = alist[rightmark]

           alist[rightmark] = temp

   temp = alist[first]

   alist[first] = alist[rightmark]

   alist[rightmark] = temp

   return rightmark

alist = [54,26,93,17,77,31,44,55,20]

quickSort(alist)

print(alist)

selection sort:

def selectionSort(alist):

   for fillslot in range(len(alist)-1,0,-1):

       positionOfMax=0

       for location in range(1,fillslot+1):

           if alist[location]>alist[positionOfMax]:

               positionOfMax = location

       temp = alist[fillslot]

       alist[fillslot] = alist[positionOfMax]

       alist[positionOfMax] = temp

alist = [54,26,93,17,77,31,44,55,20]

selectionSort(alist)

print(alist)

Shell sort:

def shellSort(alist):

    sublistcount = len(alist)//2

    while sublistcount > 0:

      for startposition in range(sublistcount):

        gapInsertionSort(alist,startposition,sublistcount)

      print("After increments of size",sublistcount,

                                   "The list is",alist)

      sublistcount = sublistcount // 2

def gapInsertionSort(alist,start,gap):

    for i in range(start+gap,len(alist),gap):

        currentvalue = alist[i]

        position = i

        while position>=gap and alist[position-gap]>currentvalue:

            alist[position]=alist[position-gap]

            position = position-gap

        alist[position]=currentvalue

alist = [54,26,93,17,77,31,44,55,20]

shellSort(alist)

print(alist)