The notion of the current working directory (CWD) turns out to be a key concept in some scripts’ execution: it’s always the implicit place where files processed by the script are assumed to reside unless their names have absolute directory paths. As we saw earlier, os.getcwd lets a script fetch the CWD name explicitly, and os.chdir allows a script to move to a new CWD.

Keep in mind, though, that filenames without full pathnames map to the CWD and have nothing to do with your PYTHONPATH setting. Technically, a script is always launched from the CWD, not the directory containing the script file. Conversely, imports always first search the directory containing the script, not the CWD (unless the script happens to also be located in the CWD). Since this distinction is subtle and tends to trip up beginners, let’s explore it in a bit more detail.