我们可以在Python中使用os.listdir获得时间戳信息（例如ls -l）吗？

Question

I contact an SFTP server and show files based on the modified timestamp.

Currently, it is done using something like:

1. files = os.listdir(SFTP)
2. Loop over files and get the timestamp using os.stat .
3. Sort the final list in Python.

This looping in Step 2 is very costly when the SFTP is on a different server because it has to make a network call from the server to the SFTP for each and every file.

Is there a way to get both the file and modified time using os.listdir or a similar API?

I am using a Windows back-end and the SFTP connection usually is done using the win32wnet.WNetAddConnection2 package. A generic solution would be helpful, if not a specific solution should be fine too.

Answer 1

You should use special libraries for this, such as sftp or ftplib , they provide specific utils that will be helpful for you. Also, you can try to call the interesting command on the server.

Answer 2

If youre able to send one line commands to the server, you could do [os.stat(i) for i in os.listdir()]

If that doesn't work for you, I suppose you could just do os.system("ls -l")

If neither of those work, please do tell me!

Answer 3

If you're using Windows, you've got a lot to gain to use os.scandir() (python 3.5+) or the backport scandir module: scandir.scandir()

That's because on Windows (as opposed to Linux/Unix), os.listdir() already performs a file stat behind the scenes but the result is discarded except for the name. Which forces you to perform another stat call.

scandir returns a list of directory entries, not names. On windows, the size/object type fields are already filled, so when you perform a stat on the entry (as shown in the example below), it's at zero cost:

(taken from https://www.python.org/dev/peps/pep-0471/ )

def get_tree_size(path):
    """Return total size of files in given path and subdirs."""
    total = 0
    for entry in os.scandir(path):
        if entry.is_dir(follow_symlinks=False):
            total += get_tree_size(entry.path)
        else:
            total += entry.stat(follow_symlinks=False).st_size
    return total

so just replace your first os.listdir() call by os.scandir() and you'll have all the information for the same cost as a simple os.listdir()

(this is the most interesting on Windows, and a lot less on Linux. I've used it on a slow filesystem on Windows and got a 8x performance gain compared to good old os.listdir followed by os.path.isdir in my case)