Bulk renaming of files based on lookup

Question

I have a folder full of image files such as

• 1500000704_full.jpg
• 1500000705_full.jpg
• 1500000711_full.jpg
• 1500000712_full.jpg

Answer 1

A rewrite of Wesley's using generators:

import os, os.path

with open('mapping.txt') as mapping_file:
    mapping = dict(line.strip().split() for line in mapping_file)

rootextiter = ((filename, os.path.splitext(filename)) for filename in os.listdir('.'))
mappediter = (
    (filename, os.path.join(mapping[root], extension))
    for filename, root, extension in rootextiter
    if root in mapping
)
for oldname, newname in mappediter:
    os.rename(oldname, newname)