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Introduction to Python Basics

Hello everyone, welcome to our new series on Python which will prep you for Python Exploitation Development, Automation and Application Management! Today's Blog out of many to come will be the basics and nothing too hard, so if you're aware of this please skip this blog unless you want to refresh your memory.

What will be covered?

  1. The print() function, what they are and examples
  2. Variables, what they are and examples
  3. The input() function, what they are and examples
  4. Operators two types, what they are and examples
  5. Random parts like importing a module, pip etc
  6. A challenge for you to complete with the knowledge you gained.

Just basic knowledge

When we're using Python, we will use functions and these functions will always have parenthesise's "()"

When we're using strings they will always be wrapped in double quotes or single quotes for example using a string with a variable

s = 'hello'
d = "hello"

Importing a module

import module_name
import module_name
or 
import module, module2, etc

Installing pip and using pip (Debian)

What is pip? Pip is a Python Package Manager that allows you to install packages, dependencies that didn't come with the original pre-filled Modules and Dependencies.

Install:

sudo apt-get install python3-pip

Syntax:

python3 -m pip install package_name
python3 -m pip install SomePackage>=version # Specific Version
python3 -m pip install "SomePackage>=version" # Minimum Version 
# Upgrading a package
python3 -m pip install --upgrade SomePackage

The print() function is one of the most commonly used functions in Python because it's role is to display text, responses etc on a terminal, for example, if I wanted to output "Hello I am a hacker" onto someone's terminal I could simply use the following syntax

print("Hello I am a hacker")

We can also work with multi-line which is a thing in Python that allows us to print onto a new line for example if I wanted to print the following message

print("Hello, I am John!
I am learning Python")

image.png

This would cause an error due to the fact that there is no end double/single quote or parenthesise thus causing an error although we ended it on the next line the function does not know how to read that it only knows how to read one line strings so we use a "multi-line" example syntax

print("""Hello, I am John!
I am learning Python""")

image.png

What is a variable? A variable is nothing more and nothing less than something that holds a value such as a user input or a function, this input can be hardcoded too. Why would we need a variable you may ask? We use variables when we're wanting to keep stuff clean and short while re-using the value of that variable.

Example syntax:

variable_name = "Hello"
print(variable_name)

We can now continue writing our code and then later on instead of having to use print("Hello") we can do a short variable name like x and print(x) which will print the value of that variable in our case "Hello" however, you cannot use this variable in a print() function the variable has been defined below the actual attempt at printing the variable name.

E.g.

print(var)
var = "Hello"

This will cause an error because the variable has not been defined before we try calling it.

input() function + print()

The input() function is a function that allows us to take user input for example if we wanted to receive the users name we could ask them to enter a value. Let's take a look at an example:

input("What is your name?:")

image.png

Cool but you may be asking how can we use this? Well, variables can come in place to store the user input data and then we can relay that later for example:

name = input("What is your name?:") #ask the user for their name
print(name) #print back the values they entered

image.png

The input() function also has a method called int() which only parses integer values (numbers not decimals) for example

inte = int(input("Enter an age:")) # integer input
print(inte) #print the value

Operators (Two Types)

Arithmetic Operators

We can multiply, Add and Subtract numbers together with Python (As seen below we can do more) Why would we need this? For example, you've been asked to build a basic calculator you'd want to know this.

image.png

Example syntax:

x = 10
f = 20 
print(f + x)

You might have realised I haven't strung the values for the variable x and f this is because if I do it'll be parsed as a string which would not add together but instead print out 1020 which isn't 10+20.

Multiplication Example:

x = 20
f = 30 
print(x * f)

image.png

Assignment Operators:

An assignment operator is used when we want to pre-define an operator to a number, for example, if we have a variable with the value of 10 but want to multiply it by 20 we could use an assignment operator without using the print() function to do so thus helps us work more productively.

![image.png] (cdn.hashnode.com/res/hashnode/image/upload/..)

Syntax:

x = 50
f = 30 
f*= 30 # Multiples f by 30
print(x+f)

The original value of f is 30 however we multiplied the value by itself.

Comparison Operators

A Comparison Operator compares a value to another value for example if we wanted to check if a variable is equal or was more than the number stored in the variable we could do so.

x = 10
f = 30
print(x > f)

This defines two variables called x which has the value of 10 and f which has the value of 30 we then do print(x > f) "x > f" is saying is x greater than f which returns false.

image.png

Challenge

The challenge is to create a calculator that takes two numbers from a user, stores them and then multiplies the number then outputs the number.

If you struggle with this challenge read the two parts #1 variables #2 input() function + print() #3 Arithmetic Operators.

The end

I hope you enjoyed this short blog. I will be retweeting everyone that tweets me a picture of their calculators! @RiotSecTeam

The next blog will be stuff like conditions, statements and building our first game then after that we will move on to Exploit Writing, Application Development and automation!

Twitter:twitter.com/RiotSecTeam

 
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