contributors

SOURADEEP DE

IRC Nick: souradeep

@desouradeep

FOSS CONTRIBUTOR :

CURRENTLY:

AVIK GHOSH

IRC Nick: avik

@neonONtheRocks@

FOSS CONTRIBUTOR :

Python For You and Me, Kushal Das

CURRENTLY:

SUDIP MAJI

IRC Nick: iamsudip

@iamsudip258

FOSS CONTRIBUTOR :

CURRENTLY:

 BODHISWATTWA TEWARI

@ZubinZorro

IRC Nick: zubin

ATISH NATH KUMAR

IRC Nick: atish

@atishnath123

 

CURRENTLY:

python is simple

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World");
    }
}

#include<stdio.h>
void main()
{
    printf("Hello World!");
} 

The Pythonic Way

Code directly in the interpreter:

>>> print "Hello World!"
Hello World!

#!/usr/bin/env python
print "Hello World!"

$ python helloworld.py
Hello World!

assignments

>>> a , b = 45, 54
>>> a
45
>>> b
54

We do not specify the datatype. We just assign, Python does the rest.

>>> a = 13
>>> b = 23
>>> a + b
36

Lets swap two numbers

>>> a = 45
>>> b = 54
>>> c = a
>>> a = b
>>> b = c
>>> print a, b
54 45

>>> a, b = b , a
>>> print a, b
54 45

control flow

• if else
  
• while
  
• for
  

IF STRUCTURE

AN EXAMPLE

if expression:
    do this

>>> x = int(raw_input("Please enter an integer: "))
>>> if x < 0:
...      x = 0
...      print 'Negative changed to zero'
... elif x == 0:
...      print 'Zero'
... elif x == 1:
...      print 'Single'
... else:
...      print 'More'

WHILE STRUCTURE

AN EXAMPLE

>>> n = 0
>>> while n < 11:
...     print n
...     n += 1
...
0
1
2
3
4
5
6
7
8
9
10

while condition:
    statement1
    statement2

LETS REVISIT FIBONACCI SERIES

THE OUTPUT

>>> a, b = 0, 1
>>> while b < 100:
...    print b
...    a, b = b, a + b

1
1
2
3
5
8
13
21
34
55
89

FOR loop

Before diving into for loops, we should get acquainted  with the range() function

>>> range(10)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> range(2,10)
[2, 3, 4, 5, 6, 7, 8, 9]
>>> range(2, 10, 3)
[2, 5, 8]

>>> for i in range(0, 5):
...     print i
0
1
2
3
4

DATA STRUCTURES

• List
  
• Tuple
  
• Dictionary

A Data structure is a way to store, retrieve and manipulate data

LISTS

A list is similar to an array but with much greater functionality.

a = [1, 2, 3]

a = ['as', 23, [1, 2, 3, 'a']]

SOME List functions

>>> a
[1, 1, 2, 7, 4, 5, 6]

>>> len(a)
7

>>> a.reverse()
[6, 5, 4, 7, 2, 1]

>>> a.count(1)
2

>>> a.sort()
[1, 1, 2, 4, 5, 6, 7]

>>> a.insert(2, 9)
[1, 1, 9, 2, 4, 5, 6, 7]

>>> del a[-1]
[1, 1, 9, 2, 4, 5, 6]

LOOPING ACROSS LISTS

Yeah, its that simple :)

>>> languages = ['Python', 'C', 'Java', 'Ruby']
>>> for i in languages:
...     print i
Python
C
Java
Ruby

LETS IMPLEMENT STACK AND QUEUE USING LISTS

>>> a = [1, 2, 3, 4, 5]
>>> a.append(1)
>>> a
[1, 2, 3, 4, 5, 1]
>>> a.pop(0)
1
>>> a.pop(0)
2
>>> a
[3, 4, 5, 1]

>>> a
[1, 2, 3, 4, 5, 6]
>>> a.pop()
6
>>> a.pop()
5
>>> a.append(34)
>>> a
[1, 2, 3, 4, 34]

tuple

Tuples are immutable data structures. Elements are seperated by a comma.

>>> a = 'Fedora', 'Debian', 'Kubuntu', 'Pardus'
>>> a
('Fedora', 'Debian', 'Kubuntu', 'Pardus')
>>> a[1]
'Debian'
>>> for x in a:
...     print x,
...
Fedora Debian Kubuntu Pardus

DICTIONARIES

>>> data = {'name':'Souradeep De', 'dept':'CSE'}
>>> data['name']
'Souradeep De'
>>> data['dept']
'CSE'

Dictionaries are unordered set of key:value pairs, where keys are unique

>>> data['college'] = 'BCREC'
>>> data
{'dept': 'CSE', 'college': 'BCREC', 'name': 'Souradeep De'}

FUNCTIONS

Reusing the code as much as possible

def functionname(params):
    statement1
    statement2

>>> def sum(a, b):
...     return a + b

revisiting palindrome function

>>> def palindrome(s):
...    return s == s[::-1]
>>> palindrome('abcd')
False
>>> palindrome('abccba'):
True

SOME EXCITING STUFF

No rocket science involved, only a few lines of code

DOWNLOADING A FILE

TASK:  Download the ebook, Python for You and Me, Kushal Das.

Open the current directory and search for the file "pym.pdf"

1 | from urllib import urlretrieve
2 | urlretrieve('http://kushaldas.in/tmp/pym.pdf','pym.pdf')

FACEBOOK STATUS UPDATE

TASK: Posting a Status Update on your Facebook wall

1 | import fbconsole
2 | fbconsole.AUTH_SCOPE = ['publish_actions']
3 | fbconsole.authenticate()
4 | fbconsole.post('/me/feed', {'message':'Python Rocks!!!'})
5 | fbconsole.logout()

Visit you wall and see the post.

sending an email

TASK: Send an email from your gmail account.

1 | import smtplib
2 | server = smtplib.SMTP('smtp.gmail.com', 587)
3 | server.ehlo()
4 | server.starttls()
5 | server.login('yourEmailUsername', 'yourEmailPassword')
6 | message = 'Hi, \nPython is awesome. :)\nThanks.'
7 | server.sendmail("from.email@gmail.com", 
                    "to.email@example.com", message)

This is just an example, not the actual method of sending an email, since the email will lack a subject among other fields.

DOWNLOADING PYCON US 2013 VIDEOS

1 | from requests import get
2 | from feedparser import parse
3 | from urllib import urlretrieve
4 | from os import system
5 | 
6 | req = get('http://pyvideo.org/category/33/pycon-us-2013/rss')
7 | dic = parse(req.text)
8 | for entry in dic['entries']:
9 |     try:
10|         video_link = entry.links[1]['href']
11|         print 'Downloading video', video_link
12|         if video_link.startswith('https://www.youtube.com'):      
13|             download_link = 'youtube-dl -o "%(title)s.%(ext)s" --   restrict-filenames '+ video_link
14|             system(download_link)
15|         else:
16|             download_link = video_link
17|             file_name = video_link[52:video_link.find('?')]
18|             urlretrieve(download_link, file_name)
19|     except:
20|         pass

WEB CRAWLER

TASK: Open a Firefox window and navigate to the Python Month page in PyCon India website

• Open a Firefox Window
  
• Go to google.com and search "pycon india"
  
• Click the pycon india link
  
• Go to the python month page
  

the crawler code

1 | from selenium import webdriver
2 | from selenium.webdriver.common.keys import Keys
3 | from time import sleep
4 |
5 | driver = webdriver.Firefox()	# opens firefox
6 | driver.maximize_window()
7 |
8 | driver.get('http://google.com')
9 | assert "Google" in driver.title
10| elem = driver.find_element_by_xpath('//*[@id="gbqfq"]')
11| elem.send_keys("pycon india")	# webdriver enters data in search bar
12| elem.send_keys(Keys.RETURN)	# ENTER key press
13| sleep(2)
14| # Google search results loaded
15| elem = driver.find_element_by_xpath('//*[@id="rso"]/li/div/h3/a')
16| elem.send_keys(Keys.RETURN)	# ENTER pressed on first link
17| sleep(2)
18| # PyCon India page loaded
19| elem = driver.find_element_by_xpath('/html/body/div/nav/ul/li[6]/a')
20| elem.send_keys(Keys.RETURN)	# ENTER pressed on Python Month link
21| # Python Month page loaded