Stopping the Program #
In our guess the number game, we ask the user to input their guess in each round. However, sometimes the player may want to stop the game while playing. At the moment, the player could stop the game by sending the interrupt signal to the program, which raises the KeyboardInturrupt exception. In most cases, this occurs when the user presses Ctrl+C on the keyboard, but the exact key or signal can vary depending on the platform and configuration.
Stop the game with the KeyboardInterrupt exception #
When a KeyboardInterrupt exception is raised, it interrupts the normal execution of the program and allows the user to stop the program's execution. This can be useful in situations where the program is stuck or taking too long to complete a task.
See below for an example of what happens when the player press Ctrl+C during the guess the number game execution.
Keyboard Interrupt Example
Guess the number between 1 and 100: ^CTraceback (most recent call last):
File "/Users/james/python/pythonexpert/01-guess-the-number/game.py", line 29, in <module>
game()
File "/Users/james/python/pythonexpert/01-guess-the-number/game.py", line 9, in game
guess = input("Guess the number between 1 and 100: ")
KeyboardInterrupt
Knowing that, we can update the game() function and add another try-except block to catch the KeyboardInterrupt exception within the game logic, like so:
def game():
number = random.randint(1, 100)
attempts = 0
try:
while True:
guess = input("Guess the number between 1 and 100: ")
try:
guess = int(guess)
except ValueError:
print("Invalid input! Please enter a number.")
continue
attempts += 1
if guess == number:
print(
f"Congratulations! You guessed the number in {attempts} attempts."
)
break
elif guess < number:
print("Too low. Try again.")
elif guess > number:
print("Too high. Try again.")
except KeyboardInterrupt:
print("Game interrupted. Thanks for playing!")
When the exception is caught, the program will print a message informing the user that the game has been interrupted, and the round will end, prompting the user if they would like to play another round.
❯ python game.py
Guess the number between 1 and 100: 50
Too high. Try again.
Guess the number between 1 and 100: ^CGame interrupted. Thanks for playing!
Do you want to play again? (y/n): n
Thanks for playing!
Stop the game with the player's input #
While using a KeyboardInterrupt exception to stop the round is a working solution, some players may not know that pressing Ctrl+C will stop the game, and the shortcut may be different depending on their system as well.
Instead of using the previous method, we could instead accept an additional input to stop the round.
Update the game() function to ask the player to type "s" during the number guessing step to stop the round and add another if statement to break out of the while loop:
def game():
number = random.randint(1, 100)
attempts = 0
while True:
guess = input('Guess the number between 1 and 100 or "s" to stop the round: ')
if guess.lower() == "s":
break
try:
guess = int(guess)
except ValueError:
print("Invalid input! Please enter a number.")
continue
attempts += 1
if guess == number:
print(f"Congratulations! You guessed the number in {attempts} attempts.")
break
elif guess < number:
print("Too low. Try again.")
elif guess > number:
print("Too high. Try again.")
Try and run the program again to see the result:
❯ python game.py
Guess the number between 1 and 100 or "s" to stop the round: 50
Too low. Try again.
Guess the number between 1 and 100 or "s" to stop the round: s
Do you want to play again? (y/n): n
Thanks for playing!
And this is the complete code for our number guessing game:
import random
def game():
number = random.randint(1, 100)
attempts = 0
while True:
guess = input('Guess the number between 1 and 100 or "s" to stop the round: ')
if guess.lower() == "s":
break
try:
guess = int(guess)
except ValueError:
print("Invalid input! Please enter a number.")
continue
attempts += 1
if guess == number:
print(f"Congratulations! You guessed the number in {attempts} attempts.")
break
elif guess < number:
print("Too low. Try again.")
elif guess > number:
print("Too high. Try again.")
while True:
game()
play_again = input("Do you want to play again? (y/n): ")
if play_again.lower() != "y":
print("Thanks for playing!")
break
Getting Started with Python
Data Types
Python Functions
Statements in Python
Basic Debugging in Python
Basic Algorithm
Object-Oriented Programming
Error Handling
Intermediate Algorithm
Python Modules