Modern Docker client syntax is:
docker inspect \
  -f '{{range.NetworkSettings.Networks}}{{.IPAddress}}{{end}}' container_name_or_id

Old Docker client syntax is:
docker inspect \
  --format '{{ .NetworkSettings.IPAddress }}' container_name_or_id

See https://stackoverflow.com/questions/17157721/how-to-get-a-docker-containers-ip-address-from-the-host