Intro To Python • Free Python Starter Guide
Wanting to learn Python?
Of course you do!
Python is the hacker’s language, it’s more modern than bash and it’s super cool.
If you’ve never programmed or wrote a line of code, that’s okay! We all have to start somewhere.
There’s a lot of good places to learn Python, I recommend Automate The Boring Stuff with Python and the official Python Documentation Tutorial.
If you’re learning to hack in the Cyber Security space, see Hackers Learning Path. For some project ideas, try Guessing Game and Is It Raining?
Disclaimer, you’re expected to have basic computing and operating system skills, ideally Linux.
0. Mindset • How To Python
Think about Python like any language, take English for example. There’s rules around what words can be used, their meaning, the structure of sentences and more.
All these elements are predefined and make it possible for us to learn and communicate with fellow English speaking humans.
Python is the same concept, you need to learn the rules, meanings and structure to communicate, or, create a program. Instead of humans, programming languages like Python are designed to communicate with computers.
A couple of other notes, programs are a series of instructions, programmers don’t need to know much math, you’re never too old to learn programming and programming is a creative activity.
1. Setup • Starting With Python
Start at python.org and download the latest version of the language, then use the Beginners Guide to see the options at work. Next, download a code editor, aka IDE, there are lots of options out there, I recommend Visual Studio Code. For more on Python, see Python in Visual Studio Code.
Once vscode is installed, install some extensions, use CTRL + SHIFT + x and type python it should be the first search result, just double check it's the official extension from Microsoft.
While you’re there, optionally install Beautify and GitHub.
Okay, let’s set up your folder structure, press CTRL + K O, create a new folder where ever you like, if you're unsure, go to Documents and call it Intro To Python - Mr Ash.
Now, let’s create your first python program, press CTRL + N to create a new file, then name it hello.py. The py is the python file extension, vscode will automatically detect it's a python file and save it as so.
Now, line 1, type out print('hello, world...') – this is a tradition in programming. We'll break down what is happening, but for now, just type it out and hit CTRL + S to save the file.
Let’s execute (or run) our new program and see the output. Type `CTRL + “ (that’s a tick back, it’s on the top left of your keyboard) to bring up the terminal.
Type CTRL + SHIFT + P to show the Command Palette, then type python run and hit enter on Python: Run Python File in Terminal, thanks to this article for your help.
Your output should be the following:
If something is wrong, that’s okay, welcome to bug squashing. There’s something wrong with your code, it’s not running as intended, it may be something small, like a spelling error or depending on the size of your program, an entire misconfiguration.
If all is well, great! Your first program is complete, congrats.
The program you just built is using is an expression, with the function print with a string value. I know this doesn't mean much right now, just stick with me.
Python has built-in functions, they’re like pre-built programs inside your program. It allows you to not have to write EVERYTHING from scratch. So, print() is the function that prints out, it's followed by brackets, anything inside those brackets is considered an input for the function.
In this case, we’ve passed 'hello, world...', now this is a string, one of the most common data types, we'll talk more about data types soon. Think of a string like a normal sentence, a mixture of characters including letters, spaces and/or numbers. You could put almost anything into a string, just make sure you have formatted it as so, 'string goes here'.
Okay, still with me? Great!
2. Basics • Core Python Elements
Okay, to see Python in action, we’re going to change it up slightly. Instead of creating a new file, we’re going to use an interactive shell, you’ll see what I mean.
Bring up the Command Palette with CTRL + SHIFT + P, and type python start, then select Python: Start REPL, REPL is short for Read, Eval, Print and Loop, read more if interested, and thanks to this article.
It might take a second, but you’ll notice the terminal change, this is the interactive shell.
Try your previous program, now all in one line print('hello, there...') and hit ENTER. You should see your string printed on the next line.
If you’re wondering, you don’t write complete programs here, this is for testing purposes and learning, like us!
Okay, type a new expression 2 + 2 and hit ENTER, I bet you can guess the output.
Let’s break down what’s happening. This expression includes two values, 2 and a single operator, +. The 2 values have an Integer data type, more on them soon, I promise.
Python evaluates to a single value, in this expression it’s 4, but no matter how complex a python program is, it always evaluates to a single value. You can always make a value evaluate to itself, simply type 2 and hit ENTER. For more, see Using Python as a Calculator.
Okay, so let’s learn some more elements that make up Python, we’ll do this by writing another small program.
You can switch between shells, or terminals, by selecting Python on the right.
The best way to start is always with pseudo code, this is like a plan or outline for what you expect the program to do.
- Say hello, ask for name.
- Print hello with name.
So here’s the following program:
print('Hello, world...') # Print hello
name = input('What\\'s your name? ') # Ask for name
print('Hello ' + name) # Say hello with nameDon’t forget to use the Command Palette to run the program, CTRL + SHIFT + P and type run.
The program will say hello, ask for your name and then say hello again with your name.
Let’s break this down, if you see # anything after is a comment, this is for humans, not computers. The python interpreter will see and ignore comments.
Next, on line 2, name is a variable, we could call the variable any title, but because the word name easily describes what's stored in the variable, it's a good title for it.
Think of variables like a box, we can store any value or data type inside of it. In this program, we’re storing the input from the user. input() is another built in function like print() but as you experienced, it's waiting for user interaction or input.
Line 3, uses print() again but this time it's using string concatenation, big word, it just means to combine multiple elements.
Visual Studio Code is great, like most code editors, it automatically colour codes each element of your program. In my case, variables are blue, comments are green, functions are yellow, string data types are orange and white is general syntax. Syntax just means the brackets and characters that Python uses to understand what we’re telling it to do.
Let’s learn some new data types and add them to our program. Add the following to lines 5 and 6:
age = input('What\\'s your age: ')
print(age)So we’ve added a new variable called age, it's now going to be an integer data type. Integers are whole numbers like 20, 21, 50 etc.
The output for age should be whatever you type in when asking. Now let's use some more concatenation, let's edit line 6 to look like the following:
print('You\\'re ' + str(int(age) + 1) + ' next year.')Let’s take a look at what we’ve added here. We’re using two functions inside of our print() function, there's str() and int() these are known as conversion functions. Meaning, anything that get's passed through them will be converted into their data type. This is important when we want to combine multiple data types. Python needs to know each data type, and they need to be converted into a string.
So the age variable is converted into an integer, a whole number, it adds one, and then it's converted into a string, which is normal characters, then it's combined with the other strings to form an entire sentence.
Remember, Python always evaluates to a single value. In this case, the sentence of strings is the entire value. It seems complicated at first, but after a few tries it makes more sense, don’t worry if it’s not all sticking just yet.
3. Basic Projects (Coming Soon)
This is Day 21 of #100DaysOfHacking, subscribe to the newsletter for updates and if you have feedback, message me via Twitter. Happy Hacking.
