Python Basics

By:- Ravi.Rajput

Python Basics by Ravi Rajput is licensed under aCreative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Acknowledgement

• This presentation dedicated to my mom , dad and whole family who always supported and loved me the way I am.

• I would like to thank Ashish Mistry who give me platform for sharing my knowledge

• Very much thankful to Lord Swami-Narayan

About Me• I am security researcher.• I have interest in Software

Reversing and Python Programming.• I am a noob and I learn all the

things because a noob can teach well .

Why Python?• Python is derived from many other languages,

including ABC, Modula-3, C, C++, Algol-68, SmallTalk, and Unix shell and other scripting languages.

• Easy to Learn.

• A broad standard library

• Interactive Mode

• provides interfaces to all major commercial databases.

Basic Syntax

• Print

>>>Print “Hello World..!!!”

• input

>>>raw_input(“Which scripting language is this ??”)

• comments

#This is the comment.

• Type

>>>type(port)

Variable Types

• Standard Data types• Numbers• String• List• Tuple• Dictionary

For Example:• Port = 21 # An integer

• percentage = 99.60 # A floating point

• PortName = “FTP“ # A string print counter print miles print name

Operators

• Arthmetic OperatorsSuppose a=10 and b=20

Operators Contd.

• Comparison Operators.

Suppose a=10 and b=20

Operators Contd.

• Logical Operators

Decision Making

• if>>>var=100>>If(var == 100):

Print “Inside If”

• Colon after if and indentation is compulsory.

• In if .. Else statement , If the condition is false then else part is executed.

• Nested if

• You can use if..else another if.

Loops

Loops Contd.

>>count = 0 >>while (count < 9):

print 'The count is:', count count = count + 1

• While Loop

• Else Used with While loop

>>>count = 0>>>while count < 5:

print count, " is less than 5" count = count + 1

else: print count, " is not less than 5"

• For Loop

• Output:0 is less than 5 1 is less than 5 2 is less than 5 3 is less than 5 4 is less than 5 5 is not less than 5

>>>for letter in 'Python': # First Example print 'Current Letter :', letter

>>>fruits = ['banana', 'apple', 'mango'] >>>for fruit in fruits: # Second Example

print 'Current fruit :', fruit

Loops Contd.

Current Letter : P Current Letter : y Current Letter : t Current Letter : h Current Letter : o Current Letter : n Current fruit : banana Current fruit : apple Current fruit : mango

• Output

Loops Contd.

• The break/Continue statement in Python terminates/continue the current loop and resumes execution at the next statement,

just like the traditional break found in C.

Strings>>>var1 = 'Hello World!' >>>var2 = "Python Programming“>>> print "var1[0]: ", var1[0] >>>print "var2[1:5]: ", var2[1:5]

• Output

var1[0]: H var2[1:5]: ytho

>>>var1 = 'Hello World!' >>>print "Updated String :- ", var1[:6] + 'Python'

• Output

Updated String :- Hello Python

Lists

Lists

>>>portlist=[]>>>portlist.append(21) #Appending>>>portlist.append(443)>>>portlist.append(25)>>>portlist.append(80)>>>portlist.sort() #sorting>>>print portlist #printing[21,25,80,443]>>>portlist.remove(25)#removing>>>count=len(portlist) #counting length>>>print count2>>>pos=portlist.index(21) #Indexing0

• The list in python is like an array of any data type.• There are several methods like inserting,

removing, popping, indexing, counting, sorting and reversing and it is mutable.

Tuples

• A tuple is a sequence of immutable Python objects.• The only difference between tuple and list is that can't be

changed• i.e., tuples are immutable and tuples use parentheses and

lists use square brackets.

>>>tup1 = ('phython', ‘reversing', 2013, 2014); >>>tup2 = (1, 2, 3, 4, 5 ); >>>tup3 = "a", "b", "c", "d";

• Even if tuple have single value still comma ,must be included

>>>tup=(21,)

>>>print "tup1[0]: ", tup1[0] Tup1[0]:python

>>>print "tup2[1:3]: ", tup2[1:3]Tup2[1:3]:[2,3,4]

Dictionary

Dictionary

• The python dictionary data structure provides a hash table

that can store any number of python objects and it is mutable .• The dictionary consists of pairs of items that contain a

key and value.• Each key is separated by colon and items by comma.

>>>services={‘ftp’:21,’ssh’:22,’smtp’:25,’http’:80}>>>services.keys()[‘ftp’,’smtp’,’ssh’,’http’]>>>>services.items()[(‘ftp’.21), (’http’.80), (’smtp’.25), (’ssh’.22)]>>>services.has_key(‘ftp’)True>>>services[‘ftp’]21

Functions

FunctionsYou can define functions to provide the required functionality. Here are simple rules to define a function in Python.

• Function blocks begin with the keyword def followed by the function name and parentheses ( ( ) ).

• Any input parameters or arguments should be placed within these parentheses. You can also define parameters inside these parentheses.

• The code block within every function starts with a colon (:) and is indented.

• The statement return [expression] exits a function, optionally passing back an expression to the caller. A return statement with no arguments is the same as return None.

Functions• Syntax:def function_name( parameters ):

"function_docstring" function_suite return [expression]

>>>def printinfo( arg1, *vartuple ): "This prints a variable passed arguments"

print “[+]Open_port is: “print arg1 for var in vartuple:

print var return; # Now you can call printinfo function

>>>printinfo( 21); >>>printinfo( 25,80,443);

• For example

Files

Files>>>file=open(‘portscanner.py’,’r’)>>>file.read()>>>list=file.readlines()>>>for i in list:

if ‘port’ in i:print i

>>>file.close()>>>file.open(‘sample.txt’,’w’)>>>file.write(‘overwritten’)>>>file.close()>>>file.open(‘sample.txt’,’a’)>>>file.write(‘appended’)>>>file.close()

Exception

Exception

PYTHON JAVA

try try

except catch

finally finally

raise throw

Exception>>>print 1337/0Traceback (most recent call last):

file “<stdin>”, line 1, in <module>ZeroDivisionError: Integer division or modulo by zero

try: You do your operations here;

except ExceptionE: If there is ExceptionE, then execute this block.

finally: this block is executed whether exception occur or

not.

try: file = open("testfile", "w") file.write("This is my test file for exception handling!!")

except: print "Error: can\'t find file or read data“

Finally:print ”Thank you for using this script”

Exception

Reference

1.Tutorial Points:http://www.tutorialspoint.com/python/index.htm2.Violent Python3.Learn Python: http://www.learnpython.org/

Thank you