Write a program with try-except to get two numbers as input from the user and do division operation.
 - Use try block to get input from the user and do the division of numbers.
 - Declare except handler for ZeroDivisionError and generate NameError with "ZERO DIVISON ERROR" message inside it.
 - Declare default exception handler and print the error message "ERROR CAUGHT !!!" and exit the program.
 - The program should always print "Program completed..." message at last irrespective of any errors.
 
 Scenario 1:
  Input:  
   Enter the number1: 100
   Enter the number2: 5
  Output:
   The division of 100 and 5 is 20
   Program completed...
   
 Scenario 2:
  Input:
   Enter the number1: 100
   Enter the number2: 0
  Output:
   Program completed...
   Traceback (most recent call last):
   File "C:/Users/Test/Desktop/exception.py", line 8, in <module>
    raise NameError("ZERO DIVISION ERROR")
    NameError: ZERO DIVISION ERROR
	
 Scenario 3:
  Input:
   Enter the number1: welcome
  Output:
   ERROR CAUGHT !!! (<class 'ValueError'>, ValueError("invalid literal for int() with base 10: 'asdfg'",), <traceback object at 0x05336DA0>)
   program completed...
   
Write a module named "calc.py" with below declaration and do below operations.
 Declare two variables: x=100, y=200
 Declare two functions: addition(a,b),  multiply(a,b,c)
 Print the declared variables and call functions[Ex: addition(50, 60) & multiply(2, 3, 5)] in main namespace
 Declare documentation for calc module
 
 - Import calc module and call addition() function with x and y values from module
 - Import x variable and multiply() function from calc module and call multiply() function with x,2,3 as arguments
 - Print the documentation for calc module
 
Write a package named "Phone"
Write a package named "Food" with below details
 Food/fruit.py
  Declare myfruits list with some fruit names such as apple, orange, etc.
  Declare showFruits() function which will display all the fruits in for loop.

 Food/vegetable.py
  Declare myvegetables list with some vegetable names such as carrot, tomato, etc.
  Declare showVegetables() function which will display all the vegetables in for loop.

 Food/snacks.py
  Declare mysnacks list with some snacks names such as biscuit, chocolate, etc.
  Declare showSnacks() function which will display all the snacks in for loop.
 
 Food/__init__.py
  Import snacks module
  Import showVegetables() function from vegetable module
  Import all variables and functions from fruits module
  
 Import the Food package and check the access level for variables and functions. (Direct & Sub-level)
  - Print all the variables (myfruits, myvegetables & mysnacks)
  - Call all the functions  (showFruits, showVegetables & showSnacks)
	
Write a class named "Employee" and "Company" with below details.
 Company:
  Declare constructor and store "company_name" and "company_location" details. (static)
  Declare a function named "showCompany()" which will display the company details.
  
 Employee: (Inherit 'Company' class)
  Declare constructor and store "empid", "empname" and "department" details. (Dynamic)
  Declare a function named "showEmployee()" which will display employee details.
  
 Create an object for 'Company' class and display company details.
 Create an object for first Employee and display employee and company details. (1001, Manoj, IT)
 Create an object for second Employee and display employee and company details. (1002, Suresh, Sales)
 Change the department & company_location for second employee and display the details again.
 

Write a program to get a sentence as input from the user and display the number of digits, alphabets and special characters.
 Input:
  Enter the sentence: Welcome to PYTHON. My number is 1234567890. END!!!
 Output:
  Given sentence: Welcome to PYTHON. My number is 1234567890. END!!!
  Character  Count
  ---------  -----
   DIGITS     10
   UPPER      11
   LOWER      17
   SPECIAL    12
   
Write a program to find the below math formulas. (using functions)
 Area of square (a*a)
 Area of circle (PI * r*r)
 Area of Triangle (1/2 * b*h)
 Area of Rectangle (w * h)
 
Write a program to calculate the Celsius to Fahrenheit & vice versa. (using functions)
 Input:
  Heat Calculator
  ***************
   1. Celsius to Fahrenheit
   2. Fahrenheit to Celsius
  Choose your option [1-2]: 1 
  Enter the celsius: 5

 Output:
  Celsius: 5
  Fahrenheit: 41
  
Write a program to print the ASCII value of given characters.
 Input:
  Enter the string: Welcome Python!
 Output:
  Given string: 
  ASCII Characters:
   W -> 87
   e -> 101
   l -> 108
   c -> 99
   o -> 111
   m -> 109
   e -> 101
     -> 32
   P -> 80
   y -> 121
   t -> 116
   h -> 104
   o -> 111
   n -> 110
   ! -> 33
   
Write regex to match the given pattern??
  

-------------------------------
Python
------
 http://www.diveintopython3.net/special-method-names.html

https://jcalderone.livejournal.com/32837.html

# 5a. Decrypt method
import re
def decs-trailhead.salesforce.com/users/00550000006GHTlAAO/trailmixes/VVVvbm-getting-started-with-salesforces-login.salesforce.com   m.r@in.v.c -> msalesforce1rypt(s, mydict):
  l = list(mydict.keys())
  result = ''
  for i in range(0, len(l)):
    mystr = l[i]
    if mystr == s:
      result += "'%s', " %(mydict[mystr])
    else:
      if s.startswith(mystr):
        mystr1 = mystr
        mystr1_d = mydict[mystr]
        for i in range(0, len(l)):
          if mystr1+l[i] == s:
            mystr1_d += " %s" %(mydict[l[i]])
            result += "'%s', " %(mystr1_d)
          elif s.startswith(mystr1+l[i]):
            mystr2 = mystr1
            mystr2_d = "%s %s" %(mydict[mystr1], mydict[l[i]])
            for k in range(i, len(l)):
              if mystr2+l[k] == s:
                mystr2_d += ' %s'%(mydict[l[k]])
                result += "'%s', " %(mystr2_d)
              elif s.startswith(mystr2+l[k]):
                mystr2 += l[k]
  result = re.sub(', $', '', result)
  #print("RES: [%s]"%(result))
  return '['+result+']'

print(" decrypt() method ".center(50, '*'))
print(decrypt('turing', {'turing': 'A', 'tur': 'B', 'ing': 'C', 'tu': 'D', 'ring': 'E', 'ri': 'F', 'ng': 'G'}))


# 1. check anagram
def check_anagram():
  anagram_list = []
  mydict = {}
  fp = open('C:/Users/v531997/Desktop/words.txt', 'r')
  for line in fp:
    line = line.rstrip()
    mydict[line] = False

  myresult = {}
  sorted_keys = sorted(mydict.keys())
  for i in range(0, len(sorted_keys)):
    for j in range(i+1, len(sorted_keys)):
      if mydict[sorted_keys[j]] == False and (sorted(sorted_keys[i]) == sorted(sorted_keys[j])):
        mydict[sorted_keys[i]] = mydict[sorted_keys[j]] = True
        if sorted_keys[i] in myresult.keys():
          myresult[sorted_keys[i]].append(sorted_keys[j])
        else:
          myresult[sorted_keys[i]] = [sorted_keys[i], sorted_keys[j]]

  for k in mydict.keys():
    if mydict[k] == False: myresult[k] = [k]
  
  for i in reversed(sorted(myresult.values(), key=len)): print(' '.join(i))

print(" Check Anagram ".center(50, '*'))
check_anagram()


# Skip Until
def skip_until(p,iterable):
  iterable = iter(iterable)
  skip_flag = True
  for j in iterable:
    if skip_flag:
      if p(j):
        skip_flag = False
        yield(j)
    else:
      yield(j)

print(" Skip Until ". center(50, '*'))
for i in skip_until(lambda x: len(x) > 1, ['x', 'y', 'abc', 'a', 'xyz']): print(i)


# Linked list reverse
class LN:
  def __init__(self, value, next =None):
    self.value, self.next = value, next

def str_ll(ll):
    answer = ''
    while ll != None:
        answer += str(ll.value)+'->'
        ll = ll.next
    return answer + 'None'

def reverse(ll):
  if ll == None:
    return None
  prev = None
  curr = ll
  
  while (curr != None):
    next = curr.next
    curr.next = prev
    prev = curr
    curr = next
  ll = prev
  return ll

print(" Reverse Linked List ".center(50, '*'))
l1 = LN(1, LN(2, LN(3)))
print(str_ll(l1))
print(str_ll(reverse(l1)))


# Sum of Binary tree
class TN:
  def __init__(self, value, left=None, right=None):
    self.value, self.left, self.right = value, left, right

def sums(t):
  if t == None:
    return 0
  return sums(t.left) + t.value + sums(t.right)

tree = TN(6, left=TN(3, right=TN(2)), right=TN(8, left=TN(7), right=TN(9)))
print(" Sum of Binary Tree ".center(50, '*'))
print(sums(tree))




==================
CGI
#!C:\Python27\python.exe
# httpd.conf
# Options +Indexes +FollowSymLinks +Multiviews +ExecCGI
# AddHandler cgi-script .cgi .py

import cgi
import os

def TestPage():
  print """
<html>
<head>
<title>Welcome to Python</title>
</head>
<body>
 <h3>Welcome to Python CGI</h3>
 <h4>This is my test page.</h4>
</body>
</html>
"""

def EnvPage():
  print "<html><body bgcolor='lavender'>"
  if os.environ['QUERY_STRING']:
    for myvar in os.environ['QUERY_STRING'].split('&'):
      (name, value) = myvar.split('=')
      print "<font size=3><b>{0}  -->  {1}</b></font><br>" .format(name, value)
  
  print "<center><h3>Environment Variables</h4></center><br>"
  for k in sorted(os.environ.keys()):
    print "<b>%20s</b>: %s</br>" % (k, os.environ[k])
  print "</body> </html>"

def FormPage():
  print "<html><body bgcolor='lavender'>"
  form = cgi.FieldStorage()
  first_name = form.getvalue('first_name')
  last_name  = form.getvalue('last_name')
  if first_name:
    print "<h2>Hello %s %s</h2>" % (first_name, last_name)

  print """
<form action = "/cgi-bin/sample.py" method = "post">
  First Name: <input type = "text" name = "first_name"><br/>
  Last Name : <input type = "text" name = "last_name"/>
<input type = "submit" value = "Submit" />
</form>
"""

print "Content-type: text/html\n"
#TestPage()
#EnvPage()
FormPage()
==================
Django Setup
------------

> python -m django --version
> django-admin --version

Sqlite3:
-------
> sqlite3   [<filename.db>]
 .databases
 .tables
 .schema <tab_name>
  select * from <tab_name>  [List entries without header]
  
 .show  [To display all default settings]
 .header on   [Try above query, will print header also]
 .mode column [To display output in column space separated, instead of "|" separator]
 .timer on  [To dislay the time taken to execute the query]
 .exit

	To take dump,
 > sqlite3  MyTestDb.db .dump > MyTestDB.sql
To restore from dump,
 > sqlite3  MyTestDb.db < MyTestDB.sql

To list all tables in database,
 > SELECT tbl_name FROM sqlite_master WHERE type = 'table';
 > select sql from sqlite_master WHERE type = 'table' and tbl_name = 'sample';
 > select current_timestamp as "CURRENT TIME";
 > select strftime("%d/%m/%Y %H:%M:%S  %s", 'now')
 > alter table sample add mydate text;
 > update sample set mydate = datetime('now', 'localtime')
 > select datetime(1518599385, 'unixepoch', 'localtime')

-------

> django-admin startproject MySite
> cd MySite
> python manage.py runserver 8080

To Create an application,

> python manage.py startapp myfirstapp
* Change file myfirstapp/views.py,
from django.http import HttpResponse

def sample(request):
    return HttpResponse("<h2>Hello, world!<h2> <h3>Welcome to  Django Application.</h3>")

* Create a file myfirstapp/urls.py,
from django.urls import path
from . import views

urlpatterns = [
    path('', views.sample, name='sample'),
]

* Change file MySite/urls.py
from django.contrib import admin
from django.urls import path, include

urlpatterns = [
    path('admin/', admin.site.urls),
    path('testapp/', include('myfirstapp.urls'))
]

* Start the service,
> python manage.py runserver 8080
Try URL,
 http://localhost:8080/testapp

Database Setup,
Goto MySite/settings.py
 - Change TIME_ZONE entry and database details. {Default SQLite]

# python manage.py migrate

To create super user,
> python manage.py createsuperuser

=============

# pip install pillow
https://pillow.readthedocs.io/en/3.1.x/reference/Image.html

===========
class  MyTestClass():
    a=100

    def __init__(self, funcname):
       exec("self.myval = funcname" .format(funcname=funcname))
       exec("self.{name} = 100; self.get_{name} = lambda : 12345 " .format(name=funcname))
       #exec("""def mytest(self): print("MYTEST FUNCTION")""" .format(self=self))
       #exec("self.{name} = 100; get_{name} = lambda : self.{name}" .format(name=funcname))
       
       self.keywords = ['False', 'None', 'True', 'and', 'as', 'assert', 'break', 'class', 
'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 
'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 
'nonlocal', 'not', 'or', 'pass', 'raise', 'return',     
'try', 'while', 'with', 'yield']
       print("Class object created.")
    
    #def __str__(self):
    #    print("String method: ")
    #    return "STRING: "
    
    def checkKeyword(self, keyword):
        match = 'not'
        if keyword in self.keywords:
            match = ''
        print("Given word [%s] is %s a keyword." %(keyword, match))

    def checkIdentifier(self, name):
        ## Use try / except to check NameError or SyntaxError
        isValid = False
        if str(name).isidentifier() and not str(name).startswith("_") and name not in self.keywords:
            print("Valid identifier [%s]" %(name))
        else:
            print("Invalid identifier [%s]" %(name))

    def myfunc(self):
        print("This if myfunc() function.")

    def __del__(self):
        print("Destructor called.")

    def get_a(self):
        return self.a

    def __getitem__(self):
        print("Calling getitem() method")

    def __repr__(self):
        print("MyClass(1,2,3)")
        return("rep method")

myobj = MyTestClass('myval')
myobj.myfunc()
#print(myobj)
#str(myobj, "Welcome", "welcome")
myobj.checkIdentifier('if')
myobj.checkIdentifier('abcd')
myobj.checkIdentifier('10')
myobj.checkIdentifier('_abcd')
print(myobj.a)
print(myobj.get_a())
print(dir(myobj))
print(myobj.get_myval())
repr(myobj)  #-->Triple1(a=1,b=2,c=3)
myobj.a
#print(myobj[a])
#print(myobj.mytest1())
#print(myobj.get_mynum())
#print(getattr(myobj, a))
#print(myobj.getattr(a))
del(myobj)



https://docs.python.org/3/contents.html

String -> length,
List -> length, sort, reverse, replace, min, max, count, index, data structure
Tuple -> type conversion
Dictionary ->
Set -> | & - ^
List Comprehension	-> range
Looping techniques -> enumerate, zip
Lambda expressions
Files and directories

Errors and Exceptions
Iterators, Generators, Decorators

Regular Expressions
Internet Access
Sending Email
XML and JSON Processing

Databases
Networking (Threads)
GUI Programming
Performance Monitoring (pylint, inspect)
Testing tools (unittest)

Command line argument and options (-cmvh, sys.argv, sys.path)
Python standard library
Debugging & Misc functions

Modules and Packages
Classes and OOPS

Django Framework



Static Method & Implicit properties,
This methods are visible inside classes. It can't be accessed via objects.
class MyClass():
    def __init__(self, myvar):
        self.a=myvar
        self.__b=2000

    @property
    def a(self):
        return(self.__a)

    @a.setter
    def a(self, x):
        self.__a = x
        #self.a=200
    """
    def myStaticMethod(a):
        print("This is static method. ", a)

    def myNormalMethod(self, a):
        print("This is static method. ", a)
      
myobj = MyClass()
MyClass.myStaticMethod(200)
myobj.myNormalMethod(100)
"""
myobj=MyClass(100)
print(myobj.a)
#print(myobj.b)
myobj.a=1000
print(myobj.a)

# Implicit properties
class MyClass():
    def __init__(self,x):
        self.__my_attribute = x

    def getAttribute(self):
        return self.__my_attribute

    def setAttribute(self, x):
        self.__my_attribute = x

    @property
    def my_attribute(self):
        return self.__my_attribute

    @my_attribute.setter
    def my_attribute(self, value):
        self.__my_attribute = value

myobj = MyClass(100)
#print(myobj.__my_attribute)
print(myobj.getAttribute())
myobj.setAttribute(1000)
print(myobj.getAttribute())

myobj1 = MyClass(200)
print(myobj1.my_attribute)
myobj1.my_attribute=2000
print(myobj1.my_attribute)

REF: https://www.python-course.eu/python3_properties.php
REF: http://www.bogotobogo.com/python/python_differences_between_static_method_and_class_method_instance_method.php

Profiling,
cProfile and profile provide deterministic profiling of Python programs.
A profile is a set of statistics that describes how often and for how long various parts of the program executed. 
These statistics can be formatted into reports via the pstats module.

import cProfile
import os
cProfile.run('os.getcwd()')

> python -m cProfile myscript.py
REF: https://julien.danjou.info/blog/2015/guide-to-python-profiling-cprofile-concrete-case-carbonara


Struct,
This module performs conversions between Python values and C structs represented as Python bytes objects. 
This can be used in handling binary data stored in files or from network connections, among other sources. 
It uses Format Strings as compact descriptions of the layout of the C structs and the intended conversion to/from Python values.
mypack = struct.pack('ifiii', 10, 20.5,30,40,50)
struct.unpack('ifiii', mypack)

Queue,
import queue
myqueue = queue.Queue()  # myqueue = queue.Lifoqueue(5)
for i in range(1,10): myqueue.put(i)
print(myqueue)
print(myqueue.size())
while not myqueue.empty(): print(myqueue.get())


http://structure.usc.edu/python/dist/simple-example.html
Distributing modules,
MyModule/
mymath.py
# Math module
def add(x,y): return x + y
def sub(x,y): return x - y
def mul(x,y): return x * y

setup.py
from distutils.core import setup
setup(name="mymath",
      version="1.0",
	  description="This is mymath module.",
	  author='Manojkumar R',
	  author_email='manoj.hispeed@gmail.com',
	  url='http://www.mywebsite.com/manoj',
      py_modules=["mymath"])

> python setup.py sdist

Copy the tar file and extract it to some path,
mymath-1.0.tar\dist\mymath-1.0\mymath-1.0> python setup.py install --prefix="C:\<USER>\Desktop\MySetup"
>>> sys.path.append('C:\\<USER>\\Desktop\\MySetup\\lib\\site-packages')
>>> import mymath



Regex
  match, search, sub
  Patterns -> ^ $ . [abcA-E], {}, | (), +, *, ?,  \wsd, backref [phone, date, time]
  Modifiers -> re.I, re.S

Internet Access
from urllib.request import urlopen
with urlopen('http://tycho.usno.navy.mil/cgi-bin/timer.pl') as response:
#with urlopen('https://www.unixtimestamp.com/index.php') as response:
    for line in response:
      line = line.decode('utf-8')  # Decoding the binary data to text.
      if 'EST' in line or 'EDT' in line or ' UTC' in line:  # look for Eastern Time
        print(line)

Sending Mail,
import smtplib
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText

'''
server = smtplib.SMTP('smtp.gmail.com', 587)
server.starttls()
server.login(username, pass)
 
msg = "Hi,\n\nThis is test email from python program.\n\nRegards,\nManoj"
server.sendmail("from", "to", msg)
server.quit()
'''

from_addr = 'from'
to_addr = 'to'
text = "Hi,\n\nThis is test email from python program.\n\nRegards,\nManoj"

msg = MIMEMultipart()
msg['From'] = 'from'
msg['To'] = 'to'
msg['Subject'] = 'Test Mail [Python]'
msg.attach(MIMEText(text))

server = smtplib.SMTP('smtp.gmail.com:587')
server.ehlo()
server.starttls()
server.ehlo()
server.login('user', 'pass')
server.sendmail(from_addr,to_addr,msg.as_string())
server.quit()

print "Mail Sent successfully."

Module,
""" This is my Sample module """
MYVAL=10

def myfunc():
  print("This is my function")
  print("Namespace: ", __name__)

if __name__ == '__main__':
  print("Main Function")
  print "The value of MYVAL is ", MYVAL
  myfunc()

------------
import sample
#from sample import myfunc

MYVAL=100
sample.myfunc()
print("MYVAL : ", MYVAL)
print("Module MYVAL : ", sample.MYVAL)
print(sample.__doc__)


XML,
<student_collection shelf="Student Details">
<student title="Record1">
   <regno>1001</regno>
   <name>Ramesh</name>
   <dept>CSC</dept>
</student>
<student title="Record2">
   <regno>1002</regno>
   <name>Suresh</name>
   <dept>Mech</dept>
</student>
<student title="Record3">
   <regno>1003</regno>
   <name>Aakash</name>
   <dept>CSC</dept>
</student>
</student_collection>

import xml.etree.ElementTree as ETree
tree = ETree.parse(r"Sample.xml")

root=tree.getroot()
#print("Collection: ", root.tag, "\nName: ", root.attrib)
print(root.tag.center(50, '*'))
print(root.attrib['shelf'])

for child in root:
    print("\n", child.tag, child.attrib['title'])
    print("\tRegno: ", child[0].text)
    print("\tName : ", child[1].text)
    print("\tDept : ", child[2].text)


JSON,
{
	"id": "0001",
	"dept": "CSC",
	"name": "abc",
	"marks": { "Maths": 98, "Science": 90, "English": 95 }
}

import json
json_data = json.load(open('Sample.json'))

data = {
   'name' : 'ABC',
   'id' : 1001,
   'dept': 'CSC'
}
json_str=json.dumps(data)
print(type(json_str), json_str)
json_data=json.loads(json_str)
print(type(json_data), json_data)


Networking,
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 'Connection received from from', addr
   c.send('Welcome to the Server.\nThank you for connecting...')
   c.close()                # Close the connection

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                     # Close the socket when done


Threading,
import thread
import time, os

# Define a function for the thread
def print_time( threadName, delay):
   count = 0
   while count < 5:
      time.sleep(delay)
      count += 1
      print "%s: %s [%d]" % ( threadName, time.ctime(time.time()), os.getpid() )

# Create two threads as follows
try:
   print("Program started [%d]", os.getpid())
   thread.start_new_thread( print_time, ("Thread-1", 2, ) )
   thread.start_new_thread( print_time, ("Thread-2", 4, ) )
except:
   print "Error: unable to start thread"

#while 1:
time.sleep(30)
print("Processing Completed")


Forking,
import os
def child():
   print('\nA new child ',  os.getpid())
   os._exit(0)
while True:
      newpid = os.fork()
      if newpid == 0:
         child()
      else:
         pids = (os.getpid(), newpid)
         print("parent: %d, child: %d\n" % pids)
      reply = input("q for quit / c for new fork")
      if reply == 'c':
          continue
      else:
          break

GUI Program,
import Tkinter
import tkMessageBox

top = Tkinter.Tk()

"""
## Message box with info message
def helloCallBack():
   tkMessageBox.showinfo( "Hello Python", "Hello World")

B = Tkinter.Button(top, text ="Hello")#, command = helloCallBack)
B.pack()
"""
label = Tkinter.Message(top, text = "Welcome\n\t\tto\n python")
label.pack()

top.mainloop()


Databases,
import MySQLdb
# Open database connection
db = MySQLdb.connect("localhost", "testuser", "password", "testdb" )

# prepare a cursor object using cursor() method
cursor = db.cursor()

# execute SQL query using execute() method.
sql_query="create table student(id int, name varchar(20), dept varchar(20))"
#sql_query="insert into student(id, name, dept) values(1001, 'abc', 'csc')"
#sql_query="insert into student(id, name, dept) values(1002, 'def', 'mech')"
#sql_query="update student set dept='eee' where id=1002"
#sql_query="delete from student where id=1002"
cursor.execute(sql_query)
db.commit()

# Fetch a single row using fetchone() method.
"""
sql="select * from student"
#data = cursor.fetchone()
data_set = cursor.fetchall()
for data in data_set: print(data)
"""
db.close()


Performance,
pylint -> To check the coding standard practices in code(PEP8) and detect errors.
> pip install pylint
> pylint program.py
"""welcome to python"""
import os
MYVAR = 10
print "welcome to python"
print "the value of a is: %d " %(MYVAR)
print "Name: ", os.getcwd()

Inspect -> Provides several useful functions to help get information about live objects such as modules, classes, methods, functions, tracebacks, frame objects, and code objects. 
import os
def myfunc(): print("welcome")
inspect.getdoc(os)
inspect.getfile(os)
inspect.getmodule(os)  # sys
inspect.isfunction(myfunc)
inspect.isfunction(os.getcwd)
inspect.isbuiltin(os.getcwd)

Unittest -> Framework to test/check the behaviour of functions, methods and classes
import unittest
myflag=False
myvar=30
def add(x,y):
    return x + y
   
class SimpleTest(unittest.TestCase):
   def testadd1(self):
      self.assertEqual(add(4,5),9)

   def testadd_test2(self):
       self.assertNotEqual(add(5,5), 12)
       self.assertEqual(add(5,5), 10)

   def testadd_test3(self):
       self.assertTrue(myvar)
       self.assertFalse(myflag)
       self.assertIn('p', 'python', "Match pattern not found.")
      
if __name__ == '__main__':
   unittest.main()
 

Python standard library,
 system, os, Date, Time, Math
 import calendar
 calendar.calendar(2017)
 calendar.month(2017, 5)
 import time
 time.time(); time.gmtime(); time.sleep(5)
 time.localtime(time.time()) -> [0]
 time.strftime("%Y/%m/%d %H:%M:%S", time.localtime())

Debugging & Misc functions
 alarm, sleep and exit
 hostname and login user
 Getting hostname and ip address
  socket.gethostname() | socket.gethostbyaddr(socket.gethostname())
  socket.gethostbyname(socket.gethostname())
  getpass.getuser()
  platform.platform(), platform.architecture(), platform.processor()

 Socket functions
 Executing system commands (dir|date|time \T)
 Debugger
 > python -m pdb sample.py


Errors and Exceptions
import sys
try:
    a= 10 + 20
    import asdfadf
    #raise NameError("This is raised Name Error")
except NameError as err:
    print("Caught NameError Exception: ", err)
except TypeError:
    print("Caught TypeError Exception: ", sys.exc_info()[1])
except:
    print("Caught Other Exception: ", sys.exc_info()[1])
    #sys.exit(0)
else:
    print("This is else part")
finally:
    print("Addition success")
print("Program completed")

Monkey patching -> 
http://burnignorance.com/python-tips-and-tricks/monkey-patching-in-python/
https://filippo.io/instance-monkey-patching-in-python/
Monkey-patching is the technique of swapping functions or methods with others in order to change a module, library or class behavior.
  class MyClass():
    def add(self, x, y):
      return x + y
  obj = MyClass()
  obj.add(10,20)
  def multiple(self, x, y):
    return x * y
  MyClass.add = multiple
  obj.add(10,20)

Function -> variable length args
def myfunc(a,b, c, d, e ):
    print(a,b,c,d, e)
myfunc(10,20, [30, 40, 50], **{'d':100, 'e': 200})
myfunc(10,20, *[30, 40, 50]

Executing module as script,
sample.py
def myfunc(a,b, c, d, e ):
    print(a,b,c,d, e)
myfunc(*range(50,260, 50))
if __name__ == "__main__":
    myfunc(*range(10, 60, 10))

import sample  # sys.path
sample.myfunc(*range(100,600,100))


Iterators:
  Iterator method is used to iterate elements from object as one by one.
  mylist=[10,20,30]
  for i in mylist:
    print i
  
  it = iter(mylist)
  it.next()   ##   In 3.x,  next(it)
  
Generators:
  Generators are used to generate iterators. We can use yield method to generate iterators. Normal function return value and yield return. It internally maintain refernces.
  def mygenerator():
    print "Welcome"
	for i in (10,20):
	  yield i
  it=iter(mygenerator())
  it.next()
  
  def mygenerator():
    a= yield
	yield a * 2
  it=iter(mygenerator())
  it.next()
  it.send(20)
  it.next
  
  3.0,
  def myGenerator():
	for i in range(10,50, 10): yield(i)
	
  it=myGenerator()
  next(it)  

Decorators:
  Decorator provide a very useful method to add functionality to existing functions and classes. Decorators are functions that wrap other functions or classes.
  Ex:
  def math(func, x, y):
  print "Math Function"
  func(x,y)
  
  def add(a,b):
    print "This is addition function"
    print a + b

  def mul(a,b):
    print "This is subtraction function"
    print a * b
 
  math(add, 10,20)
  math(mul,10,20)

import time
def my_decorator(myfunc):
    def my_wrapper():
      t1 = time.time()
      print("Function started ", myfunc.__name__)
      myfunc()
      print("Function ended ", myfunc.__name__)
      t2 = time.time()
      print("Time taken to execution function: ", int((t2 - t1)))
    
    return my_wrapper

@my_decorator
def myfunc():
    print("This is my function")
    time.sleep(2)

myfunc()


def my_decorator(func):
     def wrapper(*args, **kwargs):
         print("Before call")
         result = func(*args, **kwargs)
         print("After call")
         return result
     return wrapper

@my_decorator
def add(x, y, z):
    print(x, y, z)

add(100, 200, 300)

"""
def our_decorator(func):
    def function_wrapper(x):
        print("Before calling " + func.__name__)
        res = func(x)
        print(res)
        print("After calling " + func.__name__)
    return function_wrapper

@our_decorator
def succ(n):
    return n + 10

print(succ(100))
"""
  
Classes, PDF, IMAGE

Date, Time, Cal
Data Compression -> zlib, gzip
Performance Measurement -> from timeit import Timer
Testing -> unittest
Pretty print -> pprint, textwrap
Logging -> logging
Pickling and Shelving
Config Parse -> configparser
Threading & Multiprocessing
IPC and Networking -> socket, signal
GUI with Tk
Debugger -> pdb

https://docs.python.org/3/reference/index.html#reference-index
https://scipy.org/
https://www.python-course.eu/python3_namespaces.php

Exercies:
* Write a program to find the given number is odd or even number ?
  Input:
   Enter the number: 15
  Output:
   The given number(15) is odd number.

* Write a program to check whether the given string is a palindrome ?
  Input:
   Enter the string: racecar
  Output:
   The given string 'racecar' is a palindrome.
   
* Write a program to print the number histogram.
  Input:
   Enter the number for histogram: 5826
  Output:
   Result,
   *****
   ********
   **
   ******
   
* Write a program to count the number of characters(occurences) in a string.
  Input:
   Enter the string:  welcome to python program
  Output:
   a  ->  1
      ->  3
   c  ->  1
   e  ->  2
   g  ->  1
   h  ->  1
   m  ->  2
   l  ->  1
   o  ->  4
   n  ->  1
   p  ->  2
   r  ->  2
   t  ->  2
   w  ->  1
   y  ->  1

=============================
Write a program to find the longest line in the given string ?
 Input:
  Enter the lines:
   welcome to python
   this is the longest line
   this is my first line
   this is second line
   short line here
   this is the end line
 Output:
  Given lines: [above lines here]
  Longest line: this is the longest line [Length: 24]

 Enhance this program to print both longest and shortest lines.
  
Write a program to calculate the sum of given numbers?
 Input:
  Enter the limit/count for numbers: 3
  Enter the number 1: 10
  Enter the number 2: 20
  Enter the number 3: 30
 Output:
  The sum of given numbers [10 20 30] is:  60

Write a program to print number histogram and get the sum of all digits in a number ?
 Input:
  Enter the number for histogram: 5826
 Output:
  The given number: 5826
  Result,
  *****
  ********
  **
  ******
  The sum of digits in number: 21
 
>>> def getNumber2(n):
	global result
	if n > 0:
		getNumber2(n/10)
		print n%10, "*" * int(n%10)
		result += n%10

>>> getNumber2(mynum)
4 ****
2 **
6 ******
7 *******
 
 
def factorial(n):
	if n <= 1:
		return n
	else:
		return n * factorial(n-1)


=============================
NOTES
Joining 2 lines,
print "welcome \
to \
python"

Multiple statements in single line,
print "welcome to python"; print "second string"

Multiple assignment,
x,y = 100, 200
a=b=123

.format method,
>>> "{:15}".format(mystr)
'python         '
>>> "{:<15}".format(mystr)
'python         '
>>> "{:*<15}".format(mystr)
'python*********'
>>> 
>>> "{:>15}".format(mystr)
'         python'
>>> "{:*>15}".format(mystr)
'*********python'
>>>
>>> "{:^15}".format(mystr)
'    python     '
>>> "{:*^15}".format(mystr)
'****python*****'
>>> "{:.3}".format(mystr)
'pyt'

>>> "{:d}".format(123)
'123'
>>> "{:5d}".format(123)
'  123'
>>> "{:f}".format(123.4567)
'123.456700'
>>> "{:.2f}".format(123.4567)
'123.46'
>>> "{:15.2f}".format(123.4567)
'         123.46'

Finding the max and minimum value from dictionary,
>>> mydict = {'x':500, 'y':5874, 'z': 560}
>>> max(mydict.values())
5874
>>> min(mydict.values())
500
>>> max_key = max(mydict.keys(), key=(lambda k: mydict[k]))
>>> print max_key, mydict[max_key]
y 5874
>>> 
>>> min_key = min(mydict.keys(), key=(lambda k: mydict[k]))
>>> print min_key, mydict[min_key]
x 500

Built-in methods,
all()
any(), etc...

To get the content from web page,
import requests
response = requests.get("https://en.wikipedia.org/robots.txt")
print response.text


To check whether the webpage is exist,
from urllib.request import urlopen
from urllib.error import HTTPError
from urllib.error import URLError
try:
    html = urlopen("http://www.example.com/")
except HTTPError as e:
    print "HTTP error"
except URLError as e:
    print "Server not found!"
else:
    print "HTML Details"
    print html.read()

=============================


Project:
Bank ATM machine Project
  Design a program to do the functionalities of Bank ATM machine.

Requirements,
 - Display "Welcome Screen" with menu options
    1. Account Summary
    2. Withdraw Amount3. Deposit Amount
	4. Mini Statement [optional]
	5. Transfer Amount [optional]
	6. Exit
 - For any option, get the card number and pin details and do the authentication [first time authentication]

 Additional,
 - Send SMS to registered mobile number
 - Send mails to registered email-id if any transaction amount is above Rs. 10000
 - For 5 invalid login attempt, block the card/account



type() - get the data type for a variable
id() - get the memory address of an object
with 

>>> mynum = input('Enter the number: ')
Enter the number: 10 + 20
>>> mynum
30
>>> type(mynum)
<type 'int'>
>>>
>>> mystr = input('Enter the string: ')
Enter the string: 'welcome ' + 'to Python'
>>> mystr
'welcome to Python'
>>> type(mystr)
<type 'str'>

>>> mynum = raw_input('Enter the number: ')
Enter the number: 10 + 20
>>> mynum
'10 + 20'
>>> type(mynum)
<type 'str'>
>>>
>>>
>>> mynum = eval(raw_input('Enter the number: '))
Enter the number: 10 + 20
>>> mynum
30
>>> type(mynum)
<type 'int'>


.py - Regular scripts
.py3 - (rarely used) Python3 script. Python3 scripts usually end with ".py" not ".py3", but I have seen that a few times
.pyc - compiled script (Bytecode)
.pyo - optimized pyc file (As of Python3.5, Python will only use pyc rather than pyo and pyc)
.pyw - Python script for Windows. It is executed with pythonw.exe
.pyx - Cython src to be converted to C/C++
.pyd - Python script made as a Windows DLL
.pxd - Cython script which is equivalent to a C/C++ header
.pxi - MyPy stub
.pyi - Stub file (PEP 484)
.pyz - Python script archive (PEP 441); this is a script containing compressed Python scripts (ZIP) in binary form after the standard Python script header
.pywz - Python script archive for MS-Windows (PEP 441); this is a script containing compressed Python scripts (ZIP) in binary form after the standard Python script header
.py[cod] - wildcard notation in ".gitignore" that means the file may be ".pyc", ".pyo", or ".pyd".


Simple syntax
Easy/Quick to develop
Fewer lines of code
Reduce development time
Dynamic data type allocation

Ask about them - 
Introduction - Collegue, Any doubt stop,
OS and Intro - 



As of 03/10/2017, (Rent Rs. 8700/2 -> 4350)
 EB bill: Rs. 265
 Total: Rs. 265  => Rs. 132
For FSaravana,
 Remaining + 2 months rent + others
 Rs. 34538 + Rs. 4350 + Rs. 132 => Rs. 39020


As of 03/11/2017, (Rent Rs. 4300/2 -> 2150)
For Saravana,
 Remaining + 1 month rent + others
 Rs. 34020 + Rs. 2150 + Rs. 0 => Rs. 36170

Rent/Owner Account,
 Bank Name:  INDIAN OVERSEAS BANK
 IFSC Code:  IOBA0000098
 Account Number:  009801000046497

Electricity Bill,
 Consumer No: 092370211213
 Name: A.MOHAMEDALI KAMARUNISSA
 Region: 09-Chennai-South
 Circle: 400-South1

We need to get the remaining EB amount (Rs. 170) from neighbor for previous bills.


EB Bill,
07/07,
Total: 380 Units -> Rs. 770 (Per Unit Rs. 2.02)
Ours : 180 Units -> Rs. 365
Rem  : 200 Units -> Rs. 405

08/09,
Total: 300 Units -> Rs. 530 (Per Unit Rs. 1.76)
Ours : 150 Units -> Rs. 265
Rem  : 150 Units -> Rs. 265

For them, Rs. 670 (last 4 months)
https://tamil.boldsky.com/home-garden/how-to/2017/did-you-know-what-should-not-kept-fridge-017611.html
https://curl.trillworks.com/

##</code><code>##

import sys, os, time
import logging
import psutil

pid_file = 'test.PID'
block_file = 'test.BLOCKED'

def createPidFile(filename):
  mypid = os.getpid()
  print("Current process ID: {0}".format(mypid))
  fp = open(pid_file, 'w')
  fp.write(str(mypid))
  fp.close()

def checkFileExist(filename):
  if os.path.isfile(filename):
    print("File [{0}] is exist." .format(filename))
    return True
  print("File [{0}] does not exist." .format(filename))
  return False

def readPidFile(filename):
  fp = open(filename, 'r')
  data = fp.readline()
  print('PID: {0}' .format(int(data)))
  return int(data)
  
def checkRunning():
  if checkFileExist(pid_file):
    pid = readPidFile(pid_file)
    if checkPidExist(pid):
      print("Process is already running...")
      sys.exit(0)
    else:
      createPidFile(pid_file)
      print("PID file created successfully...")
  else:
    print("Process is not running.")

def checkPidExist(pid):
  if psutil.pid_exists(pid):
    print("PID [{0}] is running." .format(pid))
    return True
  print("PID [{0}]does not exist." .format(pid))

checkRunning()

skip_day = '17,18,20'
run_week  = 'Mon,Tue,Wed,Thu,Fri'
start_time = '17:30'
end_time   = '19:20'

def checkRunTime():
  (week_day, day, hour, min) = time.strftime('%a:%d:%H:%M', time.localtime()).split(':')
  (hour, min) = (int(hour), int(min))
  print("Current Day and Time:  {0} {1} - {2}:{3}" .format(day, week_day, hour, min))
  
  if skip_day:
    skip_days = skip_day.split(',')
    print('Skip Days: ',skip_days)
    if day in skip_days:
      return False

  run_weeks = run_week.split(',')
  (start_hr, start_min) = [int(x) for x in start_time.split(':')]
  (end_hr, end_min)     = [int(x) for x in end_time.split(':')]
  print('Run Days : ',run_weeks)
  print('Run Time :  {0}:{1} - {2}:{3}' .format(start_hr, start_min, end_hr, end_min))
  
  #print(day, run_weeks, hour, start_hr, end_hr,  min, start_min, end_min)
  if (week_day in run_weeks) and (hour >= start_hr and hour <= end_hr):
    if ((hour == start_hr and min < start_min) or (hour == end_hr and min > end_min)):
      return False
    return True
  return False

if not checkRunTime():
  print("Runtime does not match for current run...")
  sys.exit(0)

print("Runtime matched for current run...")
while True:
  if checkFileExist(block_file):
    print('BLOCK file exist.')
    time.sleep(2)
    continue
  print("Inside Loop [{0}]" .format(os.getpid()))
  time.sleep(5)


##</code><code>##

a=500

# Simple function
def myfunc():
  #global a
  #a=100
  print "This is myfunc() function."
  #print "The value of a is ", a

# Function with args
def add(a,b):
  print "Going to add two numbers: ", a, b
  return a + b

# Function with default args
def add1(a, b=50):
  print "Going to add two numbers: ", a, b
  return a + b


# Function with variable length args
def myfunc1(a,b,c):
  print "Calling myfunc1()"
  print a,b,c

# Function with variable length args
def myfunc2(**a):
  print "Calling myfunc2()"
  print a

#myfunc()

#add(10,20)
#add(b=200, a=100)

#add1(100)
#add1(1000,2000)

mylist=[10,20,30]
#myfunc1(*mylist)
mydict={'a': 100, 'b': 200, 'c': 300}
#myfunc1(**mydict)

#myfunc2(mylist)


=====================================================
OS,
 Interface between hardware and user.
 Basic need is to do read/write operation on HW. (storage processing)
 
Tasks,
 Memory management - Main memory / virtual memory
 Process management - processor, processes, threads, cpu scheduling, process synchronize, dead locks, etc.
 File management - file/folder directory structure.
 Device management - attach/detach device, plug-play
 Security - User / Group permission, patches
 Disk Management
 System performance

Layers,
 User1, User2
 Software -> OS -> System software, Application software
 HW -> CPU, RAM, IO

Diff types of OS: 
 Windows
 Unix / Linux (RHEL, Solaris, Debian, Ubuntu, HP-UX, AIX)
 Mac / ios
 Andriod

Diagram, (unix)
  HW -> Kernel ->  Shell -> Apps, Compiler, Commands, etc

Boot Process
 BIOS
 MBR (boot loader)
 Boot loader (GRUB / LILO)
 Kernel
 Operating System
 Process (init)

Diff Languages ???
Why Python ?
 1985 - 1990 -> Guido van Rossum
 Open source -> GPL License (high level programming language)
 Latest version -> 2.7.13, 3.6.2
 Interpreted language (Compiled vs Interpreted), PVM

Who Uses??
 Google -> web search
 Youtue -> Video sharing
 Dropox
 bittorrent
 NSA -> National Search Agency
 NASA -> Scienttific program
 irobot
 Company -> intel, cisco, HP, Ibm, seagate and etc

What can we do?
 System programming -> automation, report generation, monitoring, etc
 GUI
 Web programming
 Network / Internet Programming
 Component Integration
 Database Programming
 Numeric & Scientific Program
 Gaming & Robotic
 Data Mining / Analytics & Data science

-----------------------------------------------
import sys, os, time, re
import xlrd
import logging
import MySQLdb

filename = '/home/manoj/TechTrend/Dashboard.xls'
(db_connect, db_cursor) = ('', '')
dashboardDetail = [
{'name': 'Higher Volumes', 'table': 'higher_volumes', 'range': [(2, 1), (22, 5)], 
 'columns': ('ttq_daily', 'symbol', 'ltp', 'perc_chg', 'mn_ttq_perc')}
#{'name': '15 Curr Volume Breakers', 'table': 'curr_volume_breakers', 'range': [(26, 1), (46, 6)]},
#{'name': 'SIGNALS IN MOMENTUM STOCKS', 'table': 'signals_in_momentum_stocks', 'range': [(51, 1), (71, 6)]},
#{'name': 'NEAR MONTH HIGH', 'table': 'near_month_high', 'range': [(76, 1), (90, 3)]},
#{'name': 'NEAR MONTH LOW', 'table': 'near_month_low', 'range': [(76, 5), (90, 7)]},
#{'name': 'GAINERS OF THE DAY', 'table': 'gainers_of_day', 'range': [(96, 0), (110, 4)]},
#{'name': 'LOOSERS OF THE DAY', 'table': 'losers_of_day', 'range': [(96, 6), (110, 9)]},
#{'name': 'MONTHLY VOLUMES', 'table': 'monthly_volumes', 'range': [(116, 1), (164, 4)]},
#{'name': 'MONTHLY GAINERS', 'table': 'monthly_gainers', 'range': [(116, 6), (141, 9)]},
#{'name': 'MONTHLY LOOSERS', 'table': 'monthly_losers', 'range': [(145, 6), (164, 9)]}
]

def main():
  checkFileExist(filename)
  openDbConnection()
  processExcelData()
  sys.exit(0)

def processExcelData():
  global db_connect, db_cursor
  try:
    workbook = xlrd.open_workbook(filename)
    print "No of sheets in workbook", workbook.nsheets
    worksheet = workbook.sheet_by_index(0)
    print "Total No. of rows: ", worksheet.nrows
    for dashboard in dashboardDetail:
      table = dashboard['table']
      print "\nName: ", dashboard['name']
      print "Table: ", table
      print "Range: ", dashboard['range']
      (srow, scol) = (dashboard['range'][0][0], dashboard['range'][0][1]) 
      (erow, ecol) = (dashboard['range'][1][0], dashboard['range'][1][1]) 

      query="insert into %s(%s) values " %(table, ', '.join(dashboard['columns']))
      print "QUERY: ", query
      for i in range(srow, erow):
        #print "\nROW [%d] : " %(i),
        k=0
        query += '('
        for j in range(scol-1, ecol):
          value = worksheet.cell(i, j).value
          query += "'{0}'," .format(value)
        query = re.sub(',$', '), ', query)
      query = re.sub(', $', '', query)
      print "QUERY: ", query

      last_updated_time = executeQuery("select max(created_time) from %s where active='Y'" %(table), True)
      update_query = "update %s set active='N' where active = 'Y' and created_time <= '%s'" %(table, last_updated_time)
      print "QUERY: ", update_query
      executeQuery(update_query)
      executeQuery(query)
    #print "[HEADER] -> ", worksheet.row_values(0)
    #for row in range(1, worksheet.nrows):
    #  print "[DATA] -> ", worksheet.row_values(row)
      
  except:
    print "Exception caught", sys.exc_info()[1]
  db_connect.commit()
  db_connect.close()
  print "Database connection closed successfully."


def executeQuery(query, Return=False):
  global db_connect, db_cursor
  print "Query: ", query
  #return
  try:
    db_cursor.execute(query)
    if Return:
      data = db_cursor.fetchone()
      print "DATA: ", data
      return data[0]
  except:
    print "Exception caught.", sys.exc_info()[1]


def openDbConnection():
  global db_connect, db_cursor
  try:
    db_connect = MySQLdb.connect("trendz.com","trend_d","dat17","trend_d" )  ## CHANGE MYSQL ##
    print "Database connection established successfully."
    db_cursor = db_connect.cursor()
    print "Cursor object created successfully."
  except:
    print "Unable to establish connection with database. Error: ", sys.exc_info()[1]
    sys.exit(0)

## To check the existence of file
def checkFileExist(filename):
  if not os.path.isfile(filename):
    print "File does not exist. [%s]" %(filename)
    sys.exit(0)


main()

---------------------------------
def running_count(iterable,p):
  match_count = 0
  it = iter(iterable)
  while True:
    try:
        if p(next(it)):
            match_count += 1
        yield(match_count)
    except StopIteration:
        return
         
def stop_when(iterable,p):
  it = iter(iterable)
  while True:
    try:
        myval = next(it)
        if p(myval):
           return
        yield(myval)
    except StopIteration:
        return

def yield_and_skip(iterable):
  it = iter(iterable)
  while True:
    try:
        myval = next(it)
        if str(myval).isdigit():
            [next(it) for i in range(myval)]
        yield(myval)
    except StopIteration:
        return

def windows(iterable,m,n=1):
  it = iter(iterable)
  tmplist = []
  while True:
    try:
        if len(tmplist) > 0:  tmplist = tmplist[n:m]
        tmplist.extend([next(it) for i in range(len(tmplist), m)])
        yield(tmplist)
    except StopIteration:
        return

def alternate(*iterables):
  iterables = [iter(it) for it in iterables]
  while True:
    for it in iterables:
      try:
        yield(next(it))
      except StopIteration:
        return

def myzip(*iterables):
  iterables = [iter(it) for it in iterables]
  while True:
    tmplist = []
    for it in iterables:
      try:
        tmplist.append(next(it))
      except StopIteration:
        tmplist.append(None)
    if all(v is None for v in tmplist): return
    yield(tmplist)

class Backwardable:
    def __init__(self,iterable):
        self._iterable = iterable
            
    def __iter__(self):
        class B_iter:
            def __init__(self,iterable):
                self._all      = []
                self._iterator = iter(iterable)
                self._index    = -1 # index of just returned value from __next__ or __prev__
        
            def __str__(self):
                return '_all={}, _index={}'.format(self._all,self._index)
        
            def __next__(self):
                if len(self._all) == 0:
                    while True:
                        try:
                            self._all.append(next(self._iterator))
                        except:
                            break
                '''
                if len(self._all) == self._index +1:
                    try:
                        self._index +=1
                        self._all.append(next(self._iterator))
                    except :
                        self._index-=1 
                        raise
                else:
                    self._index+=1
                return self._all[self._index]      
                '''
                if self._index < len(self._all) -1 :
                  self._index += 1
                  return self._all[self._index]
                raise(StopIteration("Stop the iteration. No more next values !!"))


            def __prev__(self):
                #print(self._index)
                if self._index <= 0: 
                    raise(AssertionError("Assertion error caught. No more previous values !!"))
                self._index -= 1
                return self._all[self._index]
                
                '''
                self._index -=1
                try:
                    assert self._index> -1, 'No more previous value.'
                except AssertionError:
                    self._index+=1
                    raise
                return self._all[self._index]
               '''
        return B_iter(self._iterable)

def prev(x): return x.__prev__()


if __name__ == '__main__':
    # Test running_count; you can add your own test cases
    print('\nTesting running_count')
    for i in running_count('bananastand',lambda x : x in 'aeiou'): # is vowel
        print(i,end=' ')
    print()
    
    for i in running_count(hide('bananastand'),lambda x : x in 'aeiou'): # is vowel
        print(i,end=' ')
    print()
    
    print(nth(running_count(primes(),lambda x : x%10 == 3),1000))
    
    
    # Test stop_when; you can add your own test cases
    print('\nTesting stop_when')
    for c in stop_when('abcdefghijk', lambda x : x >='d'):
        print(c,end='')
    print()

    for c in stop_when(hide('abcdefghijk'), lambda x : x >='d'):
        print(c,end='')
    print('\n')

    print(nth(stop_when(primes(),lambda x : x > 100000),100))


    # Test group_when; you can add your own test cases
    print('\nTesting yield_and_skip')
    for i in yield_and_skip([1, 2, 1, 3, 'a', 'b', 2, 5, 'c', 1, 2, 3, 8, 'x', 'y', 'z', 2]):
        print(i,end=' ')
    print()
    
    for i in yield_and_skip(hide([1, 2, 1, 3, 'a', 'b', 2, 5, 'c', 1, 2, 3, 8, 'x', 'y', 'z', 2])):
        print(i,end=' ')
    print()

    print(nth(yield_and_skip(primes()),5))

    
    # Test windows; you can add your own test cases
    print('\nTesting windows')
    for i in windows('abcdefghijk',4,2):
        print(i,end=' ')
    print()
    
    print('\nTesting windows on hidden')
    for i in windows(hide('abcdefghijk'),3,2):
        print(i,end=' ')
    print()
    print(nth(windows(primes(),10,5),20))
    

    # Test alternate; add your own test cases
    print('\nTesting alternate')
    for i in alternate('abcde','fg','hijk'):
        print(i,end='')
    print()
       
    for i in alternate(hide('abcde'), hide('fg'),hide('hijk')):
        print(i,end='')
    print()
       
    for i in alternate(primes(20), hide('fghi'),hide('jk')):
        print(i,end='')
    print()
    print(nth(alternate(primes(),primes()),50))


    # Test myzip; add your own test cases
    print('\nTesting myzip')
    for i in myzip('abcde','fg','hijk'):
        print(i,end='')
    print()
       
    for i in myzip(hide('abcde'), hide('fg'),hide('hijk')):
        print(i,end='')
    print()
       
    for i in myzip(primes(20), hide('fghi'),hide('jk')):
        print(i,end='')
    print('\n')
    print(nth(myzip(primes(),primes()),50))

    
       

    # Test Backwardable; add your own test cases
    print('\nTesting Backwardable')
    s = 'abcde'
    i = iter(Backwardable(s))
    print(i)
    print(next(i),i) #a
    print(next(i),i) #b
    print(next(i),i) #c
    print(prev(i),i) #b
    print(prev(i),i) #a
    try:
        print(prev(i),i)
    except AssertionError:
        print('Tried to prev before first value')
    print(next(i),i) #b
    print(next(i),i) #c
    print(next(i),i) #d
    print(next(i),i) #d
    try:
        print(next(i),i)
    except StopIteration:
        print('Correctly raised StopIteration')

------------------------------------


Python Pandas and Numpy,
https://www.hackerearth.com/practice/machine-learning/data-manipulation-visualisation-r-python/tutorial-data-manipulation-numpy-pandas-python/tutorial/

IOT,
https://www.element14.com/community/groups/internet-of-things/blog/2017/02/17/iot-with-python-essential-packages

sdcard,
http://www.toontricks.com/2017/07/ubuntu-changes-to-sd-card-undone-after.html
https://superuser.com/questions/795034/format-a-protected-corrupted-sd-card
https://ubuntuforums.org/showthread.php?t=1985599
https://askubuntu.com/questions/262892/changes-to-sd-card-undone-after-re-mount-e-g-deleted-files-re-appear