Python 101 Part 3

Python 101 Part 3

May 13, 2020   Python,

We back again. we dive straight into loops.
In python we have 2 major loops: 

• While loop
• For loop (Mostly used)

WHILE LOOPS

With while loops, statements are executed while the conditions are True. 

e.g

i = 0

while i < 0:

    i+=1

    print(i)

let me breakdown down the code snippet:

• i = this is the variable. It is the indexing .
• while i < 0: = this is the statement which will be checked whether it checks out to True.
• i+=1 = this is to be executed when the condition doesn't check out to True.
• print(i) = displays output of the executed code.

Break

we use break to stop the loop amid the execution once a certain condition is met or check out to be True.

e.g 

i = 0

while i < 10:

  i+=1

  print(i)

  if i == 5:

      break

      print("You are halfway there")

 i +=1

Continue

continues with the execution even if the condition is True.

i = 0 

while i < 10:

i += 1

if (i == 5 ):

print(i,"You are halfway there")

continue

print(i)

Else

runs a the code when the condition is not True

i = 0 

while i < 10:

print(i)

i += 1

else:

print(i,"i is greater than 10")

FOR LOOP

A programmers' favorite loop because it loops everything :-), Anyway a for loop is a loop which iterates a sequence.

The difference between a for loop and a while loop is that a for loop doesn't require indexing unlike a while loop which you must provide a n indexing(Base of the loop).

Looping through a string.

e.g 

for x in "aimsec":

print(x)

let me break down this statement:

• for x in "aimsec": = this is the statement
• print(x) = this will print each and every character in the string "aimsec"

Break

With break, we can stop the looping before it has completed.

e.g

for x in "aimsec":

print(x)

if (x == "s"):

print("we stop here")

break

let me break it down:

• for x in "aimsec" = this statement iterates the string "aimsec" and assigning each character to x as a variable.
• print(x) = prints the variable
• if( x == "s") = this sets up a condition that if x == "s"
• print("We stop here") = this code is executed after which the condition is True
• break = this stops the iteration because the condition is True.

Continue

Were there is a break continue never misses.  :-), we use continue to continue the iteration after a condition is met in a loop.

e.g

for x in "aimsec":

if (x == "s"):

print(x, "is omitted")

continue

print(x)

Range( )

loops through a sequence from 0 to a specific number and increments by 1. 

for x in range(5):

print(x)

and in order to set a specific starting point in range you'll have to parse two arguments in the range function. e.g range(2, 5)

and for setting an incrementing value in the range, we parse 3 arguments e.g range(2, 5, 2)

Else

Executes a block of code when the loop is finished. e.g

for x in "aimsec":

print(x)

else:

print("Loop is complete")

Nested Loops

This is simply a loop inside a loop, whereby the inner loop is executed once at each iteration of the outer loop. e.g

for x in "aim":

for y in "sec":

print(x,y)

Pass

used instead of  empty space. and returns nothing :-)

e.g 

for x in "aimsec":

pass

Exercise: look into python conditional statements e.g IF, ELIF, ELSE
Stay tuned tomorrow we doing the IF statements.ADIOS!

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Python 101 part 2

Python 101 part 2

May 11, 2020   Python,

Back again in python programming. So we looking at List, sets, tuples and Dictionaries today.

Lists

Is a changeable and ordered collection which supports duplicate members. Lists are written in square brackets 

e.g fruits = ["banana", "Oranges", "cherries"] As the illustration below:-

You can access the list items by using the index number, e.g print(fruits[1]) this snippet will display Oranges because is at index 1.

also we can access the list by negative indexing, this means starting from the end to the beginning of the list, e.g print(fruits[-1]) this snippet will display cherries because is at index -1.

You can also access the list by ranging, whereby you access the list from a specific index to a specific index of choice e.g print(fruits[0:2]).

Other than ranging, we can access a list through looping whereby it will print all the list values 

for x in fruits:

    print(x)

Other than accessing the list we can manipulate the list by re-declaring the index number in the list. e.g fruits[1] = "mango"

Another manipulation technique in a list, we can add items in the list by using the append( ) method, by use of this method we can only add new items at the end of the list. e.g fruits.append("guava")

Unlike append, by the use of insert( ) method, we can add new items at a specific index of choice. Remember the method insert takes 2 arguments for its functioning. e.g fruits.insert(2, "berry")

we can remove items in the list by using pop( ), clear( ), remove( ) and del( ) methods.

pop( ) method

This method removes an item at a specified index e.g fruits.pop(0) and removes the last item if index is not specified.

clear( ) method

This method clears all the items in the list. e.g fruits.clear( )

remove( ) method

This method removes the specified item e.g fruits.remove("banana")

del( ) method

This method can delete the list e.g del fruits and as well removes the specified index e.g fruits.del[1] the opposite of remove.

Exercise: Research about other list methods and try to put them in practice.

Sets

These are unordered and unindexed collection and they are identified with the curly brackets { }. e.g

set1 = { "cat", "dog", "cow"}

print(set1)

we can access a set not by indexing but by looping through the set or by use of bit wise operators(in). 

by looping

for x in set1:

    print(x)

by keyword in

print("cat" in set1)

in manipulating sets, we cant change items like list, but we can only add items by use of method add( ) and method update( ).

add( ) Method

This method adds an item in the set by appending it to the end e.g set1.add("rat")

update( ) Method

This method adds numerous items in the set. e.g set1.update([" donkey "," chicken "," fowl "])

we can remove items from the set by using the discard( ) method. Why discard because discard tends to be error free when the item to be removed doesn't exist in the set. e.g set1.discard( "donkey")

Exercise: Research about other set methods and try applying them.

Tuples

Tuples are collections which are ordered but unchangeable, and they are known for round brackets ( ).

e.g 

tup1 = ( "banana"," guava"," melon " )

print(tup1)

we can access tuples bu indexing like lists e.g print(tup1[2]) same applies to ranging and negative indexing and also the famous looping(for loop).

as we all know tuples cant me changed, but you can by conversion method, whereby you convert the tuple to a list then you add an item in the list and you convert the list back to a tuple.

e.g 

x = list(tup1)

x[2] = " oranges "

y = tuple(x)

print(y)

NB:On creating a tuple with one item you add a comma after the item or else it will become a string variable e.g tup2 = ("milk",)

you cannot remove items from a tuple but you can delete the whole tuple. e.g del tup2.

Exercise: research on other tuple methods or workarounds and keep them on practice.

Dictionaries

A python dictionary is an unordered, indexed and changeable collection which have key and values . Well know for their curly brackets { }

e.g profile = { " name " : " aineah ",

                   " country " : " Kenya ",

                   " car " : " hilux "

                }

Access of the dictionary is by key value enclosed in square brackets. e.g print(profile["name"]), also by the use of method get( ), e.g print(profile.get("name")). We can also access a dictionary by the famous loop(for loop). We can also print out all data in a dictionary by using the method value( ) in the for loop

e.g

for x in profile.values():

    print(x)

by using items we can loop all items in the dict 

e.g

for x, y in profile.items( ):

    print(x ,y)

we can change the dictionaries value by referring to its key name e.g profile["name"] = " ainea musuya" or also use the same to add a new value in the dictionary e.g profile["car color"] = " black". We can remove items from a dictionary by using the pop( ), popitem( ), del( ) and clear( ).

pop( )

This method removes a specified key from the dictionary. e.g profile.pop("name").

popitem( )

This method removes the last item inserted in the dictionary e.g profile.popitem().

del( )

this method removes a specified key name e.g del profile["car"], also removes the whole dictionary e.g del profile.

clear( )

this method empties the dictionary rendering it empty.

Exercise: research more on dictionary methods and nested dictionaries and practice on them. 

alright folks that's all for today we meet up tomorrow we look into loops.ADIOS!

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Python 101

Python 101

May 10, 2020   Python,

python

Python apart from it being a reptile, it is also a pen-testers best friend, reason being it aids in automation of your day to day pen testing activities.

Python is an interpreted high level programming language. And its a beginner language because is more of  English e.g print("I love coffee")

the above statement is a python snippet, let me break it down

print     - Its a function in python for displaying on the terminal.

( )          - Used to enclose the contents to be printed. in python 3.x is mandatory unlike python 2.x (discontinued) which wasn't.

" "         - Encloses a string to be displayed on the terminal.

If you are using windows operating system you can have python installed by browsing to https://www.python.org/ to download the latest version of python which is python 3.8.2  and if you are a Linux user python is already pre-installed.

Basics

By typing in the terminal python, you will get a prompt like this:-

python prompt

in the prompt type print("hello world" )  and you get  hello world  as the output.

hello world

you can also execute python code by saving the file ending in .py extension and execute it from the terminal with the command python hello.py.

script hello.py

Variables

Variables are data containers, which are declared by assigning values to them.

x = 10
name = "aimsec"
price = 99.9

try it on your python prompt.

variables

in order for us to see the data held in the variables we use the print function.

printing variables

Data Types

Data type is simply a classification of the value or data a variable contains, we have various data types:-

• Strings - str (This are a chain of characters) e.g x = str(" aimsec ")
• Integer - int (This are 4 byte numerical values) e.g x = int(43)
• Float - float (This are 4 byte decimal values) e.g x = float(9.99)
• Boolean - bool (This contains either True or False)

e.g isLate = True      
 print(bool(isLate))

boolean

Operators

Operators are used to perform operations on variables and values. Operators are classified into various categories:-

• Arithmetic operators
• Assignment operators
• Comparison operators
• Logical operators
• Identity operators
• Membership operators

Arithmetic Operators.

Are used to perform mathematical functions 

Operator	Name	Example
+	addition	x + y
-	subtraction	x - y
*	multiplication	x * y
/	division	x /y
%	modulus	x % y
**	Exponentiation	x ** y

Assignment Operators.

Are used to assign values to variables.

Operator	Example	Equivalent
=	x = 5	x = 5
+=	x += 5	x = x + 5
- =	x - = 5	x = x - 5
* =	x * = 5	x = x * 5
/ =	x / = 5	x = x / 5

Comparison Operators.

This operators are used to compare two values.

Operator	Name	Example
==	equal	x == y
!=	not equal	x != y
>	greater than	x > y
<	lesser than	x < y
<=	lesser than or equal to	x <= y
>=	greater than or equal to	x >= y

Logical Operators.

This operators are used in combining conditional statements.

Operator	Description	Example
and	returns true if both of the statements are true	x < 1 and y < 10
or	returns true if one of the statements is true	x < 1 or y < 10
not	returns false if the result is true	not (x < 1 and y < 10)

Identity Operators.

This operators compare objects which are similar on the same memory location.

Operator	Description	Example
is	returns true if both variables are the same object	x is y
is not	returns true is both variables are not the same object	x is not y

Membership Operators.

This operators are used to test whether a sequence is present in an object.

Operator	Description	Example
in	returns true if a sequence with the specified value is present in the object	x in y
not in	returns true if a sequence with the specified value is not present in the object	x not in y

And That's all for today guys, keep practicing on this as tomorrow will be looking into lists, tuples, sets and dictionaries.

Exercise: Create a python script that prints your name, age, and your favorite color. ADIOS!

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