Generally to get file size you use the os
module: https://docs.python.org/2/library/os.path.html#os.path.getsize.
When using ftputil
they make that an equivlant call of host.path.getsize
You can view more of the documentation for it here: http://mcdc.missouri.edu/libs/python/ftputil/ftputil.html#retrieving-information-about-directories-files-and-links
...
for root,dirs,files in recursive:
for name in files:
fullpath = host.path.join(root, name)
size = host.path.getsize(fullpath)