import shutil
root = 'F:\\python2'
for rt, dirs, files in os.walk(root):
for f in files:
fn = os.path.join(rt, f)
nfn = fn.replace('.txt', '.py').
if src in fn and fn != nfn:
shutil.move(fn, nfn)
from os import walkf = []
for (dirpath, dirnames, filenames) in walk(mypath):
f.extend(filenames)
break