Question

I’m attempting to use Paramiko (Python SSH library) to read a remote file, and iterate through the lines.

My file looks something like this:

# Instance Name      VERSION               COMMENT
Bob                  1.5                   Bob the Builder
Sam                  1.7                   Play it again, Sam

My Paramiko code looks something like this:

def get_instances_cfg(self):
    '''
    Gets a file handler to the remote instances.cfg file.
    '''
    transport = paramiko.Transport(('10.180.10.104', 22))
    client = paramiko.SSHClient()
    #client.load_system_host_keys()
    client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
    client.connect('some_host', username='victorhooi', password='password')
    sftp = client.open_sftp()
    fileObject = sftp.file('/tmp/instances.cfg','r')
    return fileObject

def get_root_directory(self):
    '''
    Reads the global instances.cfg file, and returns the instance directory.
    '''
    self.logger.info('Getting root directory')
    instances_cfg = self.get_instances_cfg()
    first_line = instances_cfg.next() # We skip the header row.
    instances = {}
    for row in instances_cfg:
        name, version, comment = row.split(None, 2)
        aeg_instances[name] = {
            'version': version,
            'comment': comment,
        }

For some reason, when I run the above, I get a StopIteration error when I run .next() on the SFTP file handler:

first_line = instances_cfg.next() # We skip the header row.
File "/home/hooivic/python2/lib/python2.7/site-packages/paramiko/file.py", line 108, in next
raise StopIteration
StopIteration

This is strange, because the instances textfile I’m reading has three lines in it – I’m using .next() to skip the header line.

When I open the file locally, using Python’s open(), .next() works fine.

Also, I can iterate through the SFTP file handler fine, and it will print all three lines.

And using .readline() instead of .next() seems to work fine as well – not sure why the .next() isn’t playing nice.

Is this some quirk of Paramiko’s SFTP file handler, or am I missing something in the code above?

Cheers,
Victor

Answer 1

The the next() function is simply calling readline() internally. The only thing that can cause a StopIteration is if readline returned an empty string (look at the code, it’s 4 lines).

Look at what the return of readline() is for your file. If it’s returning an empty string, there has to be a bug in the line-buffering algorithm used by paramiko.