使用Python重命名文件似乎不起作用（os.rename）

Question

import time, os

timestamp = time.strftime('%d.%m_%H:%M')

while True:
    print("Beginning checkup")
    print("=================")
    for fname in os.listdir("C:/SOURCE"):
        if fname.endswith(".txt"):
            print("found " + fname)
            os.rename(fname, fname.replace(fname, timestamp + ".txt"))
            time.sleep(5)

This is the code I have. What its supposed to do is look for .txt files in SOURCE and add a timestamp to the name. This somehow gives me a "FileNotFoundError". Anyone have an idea?

Answer 1

Several problems

• os.listdir returns the filename, without the path.
• timestamp has a : , you cannot use that as a file name
• you rename your files into the same one because your substitution isn't working properly!

So when renaming you have to use os.path.join to provide full path to os.rename()

The next issue is that your replacement to add a timestamp is wrong . It doesn't add the timestamp but replaces the filename completely.

fname.replace(fname, timestamp + ".txt"))

is strictly equivalent to

timestamp + ".txt"

Another minor issue is that if a file ends with .TXT it is not detected by your filter. It's better to use fnmatch module for complex wildcards. In your case, I just applied lower() .

my complete fix proposal, which inserts a timestamp on all txt files of your directory:

timestamp = time.strftime('%d_%m_%H_%M') # only underscores: no naming issues
the_dir = "C:/SOURCE"
for fname in os.listdir(the_dir):
    if fname.lower().endswith(".txt"):
        print("found " + fname)
        new_name = "{}_{}.txt".format(os.path.splitext(fname)[0],timestamp)
        os.rename(os.path.join(the_dir,fname), os.path.join(the_dir,new_name))

Of course you could also os.chdir to the proper directory, but that isn't advised in a complex application because that could break other parts of the application.

You may prefer an alternative to compute absolute path & filter only on txt files using glob

import glob

for fname in glob.glob(os.path.join("C:/SOURCE","*.txt")):
   # now fname bears the absolute path