None · SyntaxShelf

Dangling Images & Orphan Volumes

syntax

# Check dangling images:
docker images -f dangling=true
# Check orphan volumes:
docker volume ls -f dangling=true

example

# Frequent rebuilds leave untagged images:
docker images -f dangling=true
# REPOSITORY  TAG     SIZE
# <none>      <none>  450MB
# <none>      <none>  450MB

# Clean them:
docker image prune
docker volume prune

Note Every time you rebuild with the same tag, the old image loses its tag and becomes <none>:<none>. These pile up fast. Volumes from removed containers also linger. Schedule regular prune commands or add them to your CI cleanup steps.

PYPython

None (Null Value)

PY · Variables & Types

syntax

variable = None

example

result = None
if result is None:
    print("No result yet")

# Common pattern: optional return
def find_user(user_id: int) -> str | None:
    return None

output

No result yet

Note Always compare to None with 'is' or 'is not', never == or !=. None is a singleton object.

DKDocker

PYPython