TryHackMe Python Simple Demo: Building Guess the Number

Python: Simple Demo

After Data Representation and Data Encoding taught how a computer stores numbers and characters, Python: Simple Demo is where you finally make it do something. It is a Pre Security room in the Software Basics module, and instead of front-loading syntax it builds one small program end to end: a Guess the Number game. The computer picks a secret between 1 and 20, you keep guessing, and it tells you too low or too high until you land it. By the time the game works you have quietly met the three pillars that hold up every imperative language: variables, conditionals, and loops.

The room ships a lab VM with VS Code and every version of the program (guess_v1.py, guess_v2.py, guess_v3.py) under /home/ubuntu/Python-Demo, so you can follow along and edit. The questions are all conceptual though, so I worked from the code itself and ran the finished game locally to check my answers.

Task 2: Variables

A variable is a labelled box that holds a value. The game needs three: secret for the hidden number, tries to count attempts, and guess for the player’s current input. The secret comes from Python’s random library, specifically random.randint(1, 20), which returns an integer in that inclusive range. The counters start at zero, and guess is seeded to a value that can never be the answer so the game does not end before it begins.

Two built-in functions do the talking. print() writes text to the screen, and reading input is a two-step move: input() returns whatever the user typed as a string, and int() converts that string into a number so it can be compared arithmetically.

secret = random.randint(1, 20)   # pick the hidden number
tries  = 0
guess  = 0

print("I'm thinking of a number between 1 and 20")   # print() displays text
text  = input("Take a guess: ")  # input() returns a string
guess = int(text)                # int() converts that string to a number
tries = tries + 1

The two Task 2 answers fall straight out of that:

• The function used to display text on the screen is print().
• The function used to convert the user’s input to an integer is int().

Task 3: Conditional Statements

A single guess is not a game. To give a hint, the program has to compare the guess against the secret and react differently in each case, and that is what conditionals are for. The logic reads like plain English: if the guess is outside 1 to 20 it is out of range; otherwise if it is below the secret it is too low; otherwise if it is above it is too high; otherwise it must be equal, so you won.

Python spells “else if” as elif, and the chain is evaluated top to bottom, stopping at the first branch that is true:

if guess < 1 or guess > 20:
    print("That number is out of range. Try again.")
elif guess < secret:
    print("Too low, try again.")
elif guess > secret:
    print("Too high, try again.")
else:
    print("You got it in", tries, "tries!")

The second Task 3 question asks what the program prints if the user enters 50. Fifty is greater than 20, so the very first condition (guess < 1 or guess > 20) is true and the rest of the chain is skipped. The output is “That number is out of range. Try again.”

Task 4: Iterations

The last missing piece is repetition. Giving the player one shot is cruel, so the program wraps the guess-and-hint block in a loop that runs until the guess matches the secret. In Python “does not equal” is !=, so the condition “keep going while the guess is wrong” is while guess != secret:. Everything indented under the while runs again and again; the moment the guess equals the secret, guess != secret becomes false and the loop exits.

The two Task 4 answers:

• The loop the program uses is a while loop.
• If the user guesses correctly on their third attempt, the else branch runs print("You got it in", tries, "tries!") with tries equal to 3, so it displays “You got it in 3 tries!”

With the loop in place the game is complete. Running the finished program reproduces the exact session the room shows in its introduction:

The whole thing is fifteen lines. The finished game is here:

Finished game on GitHub Gist: guess_the_number.py

One security-flavoured aside

This is a beginner room, but it is worth noticing the assumption hiding in int(input(...)). It trusts that whatever the user typed is a valid number. Type hello at the prompt and the program does not print a friendly message, it crashes with a ValueError, because int("hello") is undefined. That is the smallest possible version of a lesson every security-minded developer internalises: input is never trustworthy until you have validated it. A real program wraps that conversion in error handling; a toy one crashes; an insecure one does something far worse with the bad input. The habit of asking “what if the input is not what I expect” starts on exactly this line.

Room summary

Wrap-up

There is no exploit here and no flag, and that is fine. The point of the room is that a real, playable program is just three ideas stacked together: values you name and update, decisions the program makes with if / elif / else, and repetition with a while loop. Once you can read those fifteen lines and predict exactly what they print, you can read most short scripts you will meet later, whether it is an automation helper, a small exploit proof of concept, or the guts of a tool you are trying to understand. Fundamentals like this are the cheap tax you pay once so that everything after it reads faster.