Python for ethical hackersMohammad reza Kamalifardkamalifard@datasec.ir

Python language essentialsModule 1:Introduction to Python and Setting up an Environment for ProgramingPart 2 :Variables and Data Types

Variables, Objects and References• There are integers, floating point numbers, strings, and

many more, but things are not the same as in C or C++.• Python variables do not have any types associate with

them• Don’t need declaration before use• Variable name is a reference to an Object

Variables• Something which can change• Way of referring to a memory location used by a computer

program. Variable is a symbolic name for this physical location

• Memory location contains values, like numbers, text or more complicated types

Variables, Objects and References

>>> name = 'reza'

>>> print name

reza

>>>

>>>name = 10

>>>name

10

Identifier Object

Data Type>>> name = 10

>>> type(name)

<type 'int'>

>>> name = 'Reza'

>>> type(name)

<type 'str'>

>>> name = 10.42

>>> type(name)

<type 'float'>

>>>

Variables vs. Identifiers● Variables and identifiers are very often mistaken as

synonyms● The name of a variable is an identifier, but a variable is

"more than a name". ● An identifier is not only used for variables. An identifier can

denote various entities like variables, types, labels, subroutines or functions, packages and so on.

Naming Identifiers of VariablesA valid identifier is a non-empty sequence of characters of any length with:● the start character can be the underscore "_" or a capital or

lower case letter● the letters following the start character can be anything

which is permitted as a start character plus the digits.● Just a warning for Windows-spoilt users: Identifiers are

case-sensitive● Python keywords are not allowed as identifier names

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

Variables vs. Identifiers>>> name = 'reza'

>>> id(name)

3072831328L

>>> hex(id(name))

'0xb727af60L'

>>>

An other way to do that :>>> name.__repr__

<method-wrapper '__repr__' of str object at 0xb727af60>

>>>

0xb727af60 is exact memory location where the object stored, name is just a reference to that object.

Data Types Python offers1. Numbers2. Strings3. List4. Dictionaries5. Tuples6. Boolean7. …

Numbers - Integer● Normal integers

e.g. 4321● Octal literals (base 8)

A number prefixed by a 0 (zero) will be interpreted as an octal number>>> a = 010>>> print a8

● Hexadecimal literals (base 16)Hexadecimal literals have to be prefixed either by "0x" or "0X".>>> hex_number = 0xA0F>>> print hex_number2575

● Long integersthese numbers are of unlimeted sizee.g.42000000000000000000L

● Floating-point numbersfor example: 42.11, 3.1415e-10

Convert to Number>>>int('10')

10

>>>int('0011',2)

3

>>>int('1111',2)

15

>>>int('0xff',16)

255

StringsStrings are marked by quotes:

– single quotes (')'This is a string with single quotes‘– double quotes (")

"Obama's dog is called Bo""– triple quotes, both single (''') and (""")

'''String in triple quotes can extend over multiple lines, like this on, and can contain'single' and "double" quotes.'''

Strings>>>name = 'reza'

>>>name = "reza">>>name = "rez'a">>>name = 'Mohammd\nreza'

>>>print name

Mohammad

reza

Strings>>>name = r'Mohammd\nreza'

raw string and turns off escapingprint name

Mohammd\nreza

>>>

Strings>>> name = '''

... Hello Dear Students

... Welcome to PYSEC101 Course!

... Python Scripting Course for Ethical Hackers

... '''

>>> name

'\nHello Dear Students\nWelcome to PYSEC101 Course!\nPython Scripting Course for Ethical Hackers\n'

>>> print name

Hello Dear Students

Welcome to PYSEC101 Course!

Python Scripting Course for Ethical Hackers

String Index● A string in Python consists of a series or sequence of

characters - letters, numbers, and special characters.

Unicode ● Used for internationalization● “Wide Characters” are they are called(code all languages)>>>name = u'Mohammad'

>>> name

u'Mohammad'

>>>

unicode to regular string conversion>>> str(name)

'Mohammad'

>>>

regular string to unicode conversion>>> unicode(name)

u'Mohammad'

>>>

Concatenating Strings● Strings can be glued together (concatenated) with the +

operator>>>s1 + s2

>>> s1 = 'Hamid'

>>> s2 = 'rezaie'

>>> s1 + s2

'Hamidrezaie'

>>> s1 + ' ' + s2

'Hamid rezaie'

>>>

Repetition● String can be repeated or repeatedly concatenated with

the asterisk operator "*“>>> buffer = 'A' * 20

>>> buffer

'AAAAAAAAAAAAAAAAAAAA'

>>>

Int to string● >>> 'a' + 42● Traceback (most recent call last):● File "<stdin>", line 1, in <module>● TypeError: cannot concatenate 'str' and 'int' objects● >>>● >>> str(42)● '42'● >>>>'a' + str(42)

Slicing● Substrings can be created with the slice or slicing notation,

i.e. two indices in square brackets separated by a colon: ● "Python"[2:4] -> "th“● >>>string[start:end:steps]

>>> name = 'Mohammad reza'

>>> name[5:10]

'mad r'

>>> name[0:10]

'Mohammad r'

>>> name[0:-1]

'Mohammad rez'

>>> name[0:-5]

'Mohammad'

>>> name[:]

'Mohammad reza'

>>> name[::-1]

'azer dammahoM'

>>> name[::2]

'Mhma ea'

>>>

Stirngs are immutable objects>>>name = 'reza'

>>>name[0]

r

name [0] = 'a'

TypeError: 'str' object does not support item assignment

You can not change String Object directly in memory because they are immutable

>>>name = 'reza'

name = 'Mohammad'● 'reza' object still does exists now name is referenced to

'Mohammad' object

String Methods● string.find()● string.replace()● string.split()

>>> name = 'mohammad reza'

>>> name.find('PYSEC101')

-1

>>> name.find('mma')

4

>>>

>>> name.split()

['mohammad', 'reza']

by default split on white spaces and return list of strings.split on 'a'>>> name.split('a')

['moh', 'mm', 'd rez', '']

>>>

>>> name.replace('m', 'H')

'HohaHHad reza'

>>>

String Formatting>>> ip = '192.168.1.252'

>>> line = 'Crack this IP :%s' % ip

>>> line

'Crack this IP :192.168.1.252'

>>>

>>> line = 'Crack this IP : %s and name %s ' % (ip, 'Reza-PC')

>>> line

'Crack this IP : 192.168.1.252 and name Reza-PC '

ReferencesSPSE securitytube training by Vivek RamachandranSANS Python for Pentesters (SEC573)Violent pythonSecurity Power Toolspython-course.eu-----------------------------http://www.tutorialspoint.com/python/python_strings.htmhttp://www.tutorialspoint.com/python/python_numbers.htmhttp://www.python-course.eu/variables.phphttp://www.python-course.eu/sequential_data_types.phphttp://www.python-course.eu/sets_frozensets.php

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Copyright 2013 Mohammad Reza Kamalifard All rights reserved.Go to Kamalifard.ir/pysec101 to Download Slides and Course martials .