The problem is that shutil uses the statvfs
system call underneath to determine the space used. This system call has no file-path granularity as far as I'm aware, only file-system granularity. What this means is that the path you provide it with only helps to identify the file system you want to query, not the path's.
In other words, you gave it the path /data/foo/utils
and then it determined which file system backs this file path. Then it queried the file system. This becomes apparent when you consider how the used
parameter is defined in shutil:
used = (st.f_blocks - st.f_bfree) * st.f_frsize
Where:
fsblkcnt_t f_blocks; /* size of fs in f_frsize units */
fsblkcnt_t f_bfree; /* # free blocks */
unsigned long f_frsize; /* fragment size */
This is why it's giving you the total space used on the entire file system.
Indeed, it seems to me like the du
command itself also traverses the file structure and adds up the file sizes. Here is GNU coreutils du
command's source code.