I'm using ftplib to transfer files. Everything is working great. Now I'm trying to get the size of the target file before downloading.
First, I tried just getting size with ftp.size(filename). Server complained that I can't do that in ascii mode.
Then I tried setting binary mode using ftp.sendcmd("binary") and ftp.sendcmd("bin"). In both cases the server complained "500 binary Not understood"
Can ftplib get size of a file before downloading in this instance? I don't control the FTP server and can't change how it's behaving.
Thanks
Very late reply, but here's the correct answer. This works with ProFTPD.
ftp.sendcmd("TYPE i") # Switch to Binary mode
ftp.size("/some/file") # Get size of file
Ftplib can get the size of a file before downloading. As the documentation says:
FTP.size(filename) Request the size of the file named filename on the server. On success, the size of the file is returned as an integer, otherwise None is returned. Note that the SIZE command is not standardized, but is upported by many common server implementations
Apparently your server doesn't support this feature.
"Server complained that I can't do that in ascii mode." -- Try showing the exact code that you used AND the exact text of the server response. Use copy/paste, don't type from memory.
Do you have access to a command-line FTP client? If not, get one. Use it to experiment with what the server can do. A client command like REMOTEHELP is your friend. Example:
ftp> remotehelp size
214 Syntax: SIZE <sp> pathname
This indicates that the server to which I was connected will support a SIZE command.
来源：https://stackoverflow.com/questions/3231910/python-ftplib-cant-get-size-of-file-before-download