How to have Python check if a file exists and create it if it doesn't?

This one-liner will check to see if the file exists, and create it if it doesn't.

open("KEEP-IMPORTANT.txt", "a")

Similar question

This is the best way:

try:
    with open(filename) as file:
        # do whatever
except IOError:
    # generate the file

There's also os.path.exists(), but this can be a security concern.