Negation in Python

I’m trying to create a directory if the path doesn’t exist, but the ! (not) operator doesn’t work. I’m not sure how to negate in Python… What’s the correct way to do this?

if (!os.path.exists("/usr/share/sounds/blues")):
        proc = subprocess.Popen(["mkdir", "/usr/share/sounds/blues"])
        proc.wait()

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

The negation operator in Python is not. Therefore just replace your ! with not.

For your example, do this:

if not os.path.exists("/usr/share/sounds/blues") :
    proc = subprocess.Popen(["mkdir", "/usr/share/sounds/blues"])
    proc.wait()

For your specific example (as Neil said in the comments), you don’t have to use the subprocess module, you can simply use os.mkdir() to get the result you need, with added exception handling goodness.

Example:

blues_sounds_path = "/usr/share/sounds/blues"
if not os.path.exists(blues_sounds_path):
    try:
        os.mkdir(blues_sounds_path)
    except OSError:
        # Handle the case where the directory could not be created.

Method 2

Python prefers English keywords to punctuation. Use not x, i.e. not os.path.exists(...). The same thing goes for && and || which are and and or in Python.

Method 3

try instead:

if not os.path.exists(pathName):
    do this

Method 4

Combining the input from everyone else (use not, no parens, use os.mkdir) you’d get…

special_path_for_john = "/usr/share/sounds/blues"
if not os.path.exists(special_path_for_john):
    os.mkdir(special_path_for_john)

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0