TimestampScreenshot.py

from datetime import datetime
from os import path, walk
from re import search, IGNORECASE
from shutil import move

if __name__ == '__main__':
    directoryToSearch = path.join(path.expanduser('~'), 'Desktop')
    patternToTimestamp = '^(Capture|Untitled)(\.png|\.jpg|\.gif)$'
    getTimestamp = lambda: 'Screen shot ' + datetime.now().strftime("%Y-%m-%d at %H.%M.%S %p")

    for root, _, files in walk(directoryToSearch):
        for file in files:
            if search(patternToTimestamp, file, IGNORECASE):
                _, extension = path.splitext(file)
                oldPath = path.join(root, file)
                newPath = path.join(root, getTimestamp() + extension.lower())
                move(oldPath, newPath)