What is the correct way to unset a linux environment variable in python?

Just

del os.environ[MYVAR]

should work.

You can still delete items from the mapping, but it will not really delete the variable from the environment if unsetenv() is not available.

del os.environ[MYVAR]

For those who search for an elegant way to unset environment variable without errors if the variable does not exist:

os.environ.pop(MYVAR, None)

That works exactly as:

if MYVAR in os.environ:
    del os.environ[MYVAR]

But if you need to deal with the exception, do what other users suggested: del os.environ[MYVAR] or os.environ.pop(MYVAR).