Python sys.exit() method

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The Python sys.exit() method is used to terminate the execution of a program. It optionally accepts an integer or a string as an argument which is used as the exit status. By convention an argument of zero indicates successful termination while any non-zero value indicates an error.

If sys.exit() method is called with a string then the string is printed to 'stderr' before exiting. Internally it raises a SystemExit exception which can be caught to prevent the program from exiting. This method is commonly used to exit a script early due to errors or specific conditions.

Syntax

Following is the syntax and parameters of Python sys.exit() method −

sys.exit([arg])

Parameters

This method accepts a single optional parameter arg representing the exit status.

Return value

This method does not return any value.

Example 1

Following is the example of sys.exit() method which clears the cache after compiling and using some regular expressions −

import sys

print("This message will be printed.")
sys.exit(0)
print("This message will not be printed.")  

Output

This message will be printed.

Example 2

This example exits the program with status 1 indicating an error. The second print statement will not be executed −

import sys

print("An error occurred.")
sys.exit(1)
print("This message will not be printed.")  # This line will not be executed.  

Output

An error occurred.

Example 3

Here in this example we check for command-line arguments. If no arguments are provided it exits the program with a message. The message will be printed to stderr −

import sys

if len(sys.argv) < 2:
    sys.exit("No arguments provided. Exiting the program.")

print("Arguments provided. Continuing the program.")

Output

No arguments provided. Exiting the program.

Example 4

This example prompts the user to enter a positive number. If a negative number is entered it raises a ValueError and exits the program with an error message −

import sys

try:
    x = int(input("Enter a positive number: "))
    if x < 0:
        raise ValueError("Negative number entered.")
except ValueError as e:
    sys.exit(f"Error: {e}")

print("You entered a positive number.")

Output

Enter a positive number: -1
Error: Negative number entered.