Python script to delete any untagged Docker containers and images.

docker_cleanup.py

import re
import subprocess
import sys

from collections import namedtuple


def first_to_last(items):
    "Return a new list where last item in items is moved to the front"
    return items[-1:] + items[:-1]


def pad_list(items, pad_to=10, pad_with=''):
    "If items is shorter than pad_to, return a new list appending pad_with up to pad_to"
    if len(items) >= pad_to:
        return items
    return items + [pad_with for i in range(0, pad_to - len(items))]


def namedtuplify(headers, rows):
    """
    Takes a list of headers and a list of lists that are rows
    and returns a list of namedtuples.

    - removes any whitespaces in column names in headers
    - pads any rows that aren't long enough with empty strings
    """
    max_cols = len(headers)
    Row = namedtuple('Row', [col_name.replace(' ', '') for col_name in headers])
    rows = [Row(*pad_list(row, pad_to=max_cols)) for row in rows]
    return rows


def get_docker_ps():
    # save output of ps -a as list of lists, split by whitespace, and re-organized
    # so that the last column is first because ports and status columns alone are
    # optionally empty, and we only have spaces to delimit columns, so we want
    # those at the end so we can easily just pad them
    output = [
        first_to_last([i.strip() for i in line.split('  ') if i.strip()])
        for line in subprocess.check_output(['docker', 'ps', '-a']).splitlines()
        ]
    headers, rows = output[0], output[1:]
    return namedtuplify(headers, rows)


def get_docker_images():
    output = [
        [i.strip() for i in line.split('  ') if i.strip()]
        for line in subprocess.check_output(['docker', 'images']).splitlines()
    ]
    headers, rows = output[0], output[1:]
    return namedtuplify(headers, rows)


def untagged_containers(rows=None):
    "List of container ids using untagged images"
    rows = rows or get_docker_ps()
    return [i.CONTAINERID for i in rows if re.match('[0-9a-f]{12}', i.IMAGE)]


def untagged_images(rows=None):
    "List of image ids that are not tagged"
    rows = rows or get_docker_images()
    return [row.IMAGEID for row in rows if row.REPOSITORY == '<none>']


if __name__ == '__main__':
    container_ids = untagged_containers()
    image_ids = untagged_images()

    if not container_ids and not image_ids:
        print "Nothing to cleanup!"
        sys.exit()

    if container_ids:
        print "Removing containers using untagged images..."
        for container_id in container_ids:
            try:
                output = subprocess.check_output(['docker', 'rm', container_id])
            except subprocess.CalledProcessError as e:
                print e
                sys.exit()
            print output

    if image_ids:
        print "Removing untagged images..."
        for image_id in image_ids:
            try:
                output = subprocess.check_output(['docker', 'rmi', image_id])
            except subprocess.CalledProcessError as e:
                print e
                sys.exit()
            print output

    print "BOOM"