FTP client in Python

This article will show you how to use the File Transfer Protocol (FTP) with Python from a client side perspective. We use ftplib, a library that implements the FTP protocol. Using FTP we can create and access remote files through function calls.

FTP opens a control connection on TCP port 21 and then a separate data connection, which is why a login can succeed and the transfer still stall. PracticeNetworking has hands-on labs for ports, routing and firewall rules if you want to see where that breaks.

Directory listing We can list the root directory using this little snippet:

import ftplib
ftp = ftplib.FTP("ftp.nluug.nl")
ftp.login("anonymous", "ftplib-example-1")
data = []
ftp.dir(data.append)
ftp.quit()
for line in data:
    print "-", line

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This will output the directory contents. in a simple console style output. If you want to show a specific directory you must change the directory after connecting with the ftp.cwd('/') function where the parameter is the directory you want to change to.

import ftplib
ftp = ftplib.FTP("ftp.nluug.nl")
ftp.login("anonymous", "ftplib-example-1")
data = []
ftp.cwd('/pub/')         # change directory to /pub/
ftp.dir(data.append)
ftp.quit()
for line in data:
    print "-", line

Download file To download a file we use the retrbinary() function. An example below:

import ftplib
import sys
def getFile(ftp, filename):
    try:
        ftp.retrbinary("RETR " + filename ,open(filename, 'wb').write)
    except:
        print "Error"
ftp = ftplib.FTP("ftp.nluug.nl")
ftp.login("anonymous", "ftplib-example-1")
ftp.cwd('/pub/')         # change directory to /pub/
getFile(ftp,'README.nluug')
ftp.quit()

Uploading files We can upload files using the storlines() command. This will upload the file README.nluug in the main directory. If you want to upload in another directory combine it with the cwd() function.

import ftplib
import os
def upload(ftp, file):
    ext = os.path.splitext(file)[1]
    if ext in (".txt", ".htm", ".html"):
        ftp.storlines("STOR " + file, open(file))
    else:
        ftp.storbinary("STOR " + file, open(file, "rb"), 1024)
ftp = ftplib.FTP("127.0.0.1")
ftp.login("username", "password")
upload(ftp, "README.nluug")

Other functions For other functions please refer to the official library documentation.

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