Build a Python
number guessing game.

You need a Python 3 editor with console input. If variables, input or indentation are new, start with our beginner Python learning path. Save this project as guessing_game.py, not random.py: using the library’s name for your file can stop Python importing the intended module.

Write down three rules: the secret number stays the same during a game; only a valid number between 1 and 20 increases the counter; and a correct guess or quit command ends the loop. These rules give you something specific to test rather than assuming that one successful run proves the game works.

Here’s the complete game. Copy it into a Python 3 editor, save it as guessing_game.py, and run it. Then come back to unpack the decisions.

from random import randint

secret = randint(1, 20)
attempts = 0

while True:
    entry = input("Guess 1 to 20, or type quit: ").strip()
    if entry.lower() == "quit":
        print("See you next time!")
        break
    try:
        guess = int(entry)
    except ValueError:
        print("Please enter a whole number.")
        continue
    if not 1 <= guess <= 20:
        print("Stay between 1 and 20.")
        continue
    attempts += 1
    if guess < secret:
        print("Too low.")
    elif guess > secret:
        print("Too high.")
    else:
        print(f"Correct in {attempts} valid guesses!")
        break

The secret is chosen before the loop. Choosing it inside the loop would move the target after every guess. randint(1, 20) can return either endpoint. The player’s entry is text: strip() removes surrounding spaces and the quit check happens before numeric conversion.

int(entry) raises ValueError when text cannot be read as an integer. The except block gives another chance without increasing attempts. The range check also runs before the counter changes. Consequently, “hello”, “3.5”, 0 and 21 are not valid guesses in this game.

After validation, the counter increases once. The comparison selects a low, high or correct response. continue starts the next loop iteration; break leaves the loop. A while loop is appropriate because the program cannot know the number of attempts in advance.

Temporarily replace secret = randint(1, 20) with secret = 12. This makes the same test repeatable. Enter the sequence below in a single run; then restore the random line when you are finished.

In a separate run, enter “ QUIT ” with spaces to check that leaving works before numeric conversion. Also test 1 and 20 to confirm that the endpoints are accepted. If an error message unexpectedly uses an attempt, check whether you incremented the counter too early.

First add an attempt limit. Decide whether quitting should show the answer and whether invalid inputs should consume a turn; write the decision down before changing code. Next, let a player select a range, validating that the lower bound is smaller than the upper bound. Keep each version small enough to explain.

For the Python behaviour used here, consult the official randint reference and integer-conversion reference. The project code and test sequence on this page are original teaching examples. If you prefer guided projects, explore Knowledge Wave’s Programming Fundamentals course.