Something I Learned This Week — Paramiko’s Remote File Management

Another Python package to the rescue…

A couple of days ago, I was busy at my whiteboard going over the design of a new Python application that would be used to read files on my NAS (Network Attached Storage). Since it’s a fairly simple app, there was only one question that was really bugging me. How do I get Python to read a file on a remote server? Little did I know that the answer was already in front of me. On multiple past projects, I have used a package called Paramiko. According to the package website, Paramiko is a Python implementation of the SSH (Secure Shell) protocol. If you do what I did and don’t read the documentation, you’ll also discover that it can be an SFTP (Simple File Transfer Protocol) client as well. With this newfound information, I figured that Paramiko would once again answer my question. But I needed to test it first.

Reading a Remote File

Eager to see if Paramiko will save the day once more, I created a new file called remote_operations.py.

touch remote_operations.py

Once the new Python file was created, I opened it, imported Paramiko, and declared a new class:

import paramiko

class remote_operations:
     def __init__(self):
          pass

After that, I wrote a function that starts a new SSH connection:

def connect(self, hostname, username, password):
     client = paramiko.SSHClient()
     client.load_system_host_keys()
     client.connect(hostname, username=username, password=password)
     return client

The next function I wrote will start an SFTP client and open the passed file:

def open_remote_file(self, ssh_client, filename):
     sftp_client = ssh_client.open_sftp()
     file = sftp_client.open(filename)
     return file

Essentially, the open_remote_file function is the meat and potatoes of what I needed for my application to work properly. The last step to do before claiming success is to test these new functions. In order to do so, I created another file called test.py and imported the new remote_operations class within it.

from remote_operations import remote_operations

Next, I declared a new instance of the remote_operations class, called the connect function to open a new SSH session, and called the open_remote_file function.

test = remote_operations()

client = test.connect("HOSTNAME", "USERNAME", "PASSWORD")

file = test.open_remote_file(client, "/filepath/test.txt")

Lastly, I wrote some test code to loop through the lines in the file and closed the SFTP client and SSH session.

for line in file:
     print(line)

file.close()
client.close()

Sending a File For Fun

While reading the SFTP documentation, I noticed that there was a function to send a file to a remote destination. Since being able to read a remote file went pretty easily, I decided to give this put function a shot. Going off what was already in my remote_operations class, I added a new function that when copies a file to the given remote destination.

Note: The put function is only for copying local files to a remote server.

def send_file(self, ssh_client, filename, destination):
     sftp_client = ssh_client.open_sftp()
     sftp_client.put(filename, destination)
     return sftp_client

Just like when reading a file, it was necessary to check if the new send_file function will actually work. Using the already created test file, I made a call to the new function.

test = remote_operations()

client = test.connect("HOSTNAME", "USERNAME", "PASSWORD")

send = test.send_file(client, "test2.txt", "/destination/test2.txt")

send.close()
client.close()

Other Goodies

Outside of reading files and sending them to remote locations, the Paramikos SFTP client has many more functions that can be used for managing files. I won’t go into great detail about them here, but some notable ones are:

• listdir — list all items in a specified directory
• mkdir — create a new directory at a specified path
• remove — removes a specified file (only works for files)
• rmdir — removes the given directory
• rename — changes the name of a file or directory

Feel free to play around with these and see what you can get them to do!

Conclusion

To say that Paramiko is an awesome package is a clear understatement. Its many features are easy to use and can help you get something up and running very quickly. In all honesty, I was under the impression that working with remote files was going to be a programming nightmare. Fortunately, I was proven wrong by how easy it is to use Paramikos functions. Let me know in the comments how you manage remote files and if you prefer a different Python package. Until next time, cheers!

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