How to Terminate a Python Script

If you have built a Python script and would like to terminate it once it meets a condition, then you can work with the sys module and the exit() method. Let’s consider the following python script, my_simple.py, that writes a txt file.

# the 'w' mode is for write
with open('newfile.txt', mode='w') as my_file:
    
    for n in range(10):
        # add text 
        my_file.write(f'This is a line number {n}\n')
 

If we run the script in the terminal like:

python my_simple.py

We will get the newfile.txt with the following content.

This is a line number 0
This is a line number 1
This is a line number 2
This is a line number 3
This is a line number 4
This is a line number 5
This is a line number 6
This is a line number 7
This is a line number 8
This is a line number 9

Assume now, that we would like to terminate the script when the n in the for loop is greater than 4 and it is an even number. We can achieve that by adding an if statement and the sys.exit() command that terminates the script. The my_simple.py becomes:

import sys

# the 'w' mode is for write
with open('newfile.txt', mode='w') as my_file:
    
    for n in range(10):
        # add text to the new file
        my_file.write(f'This is a line number {n}\n')
        if n%2 == 0 and n>4:
            sys.exit()
 

And by running it in the command line:

python my_simple.py

We get the newfile.txt with the following content.

This is a line number 0
This is a line number 1
This is a line number 2
This is a line number 3
This is a line number 4
This is a line number 5
This is a line number 6

As you can see, the script was terminated once it met the condition.