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import json, sys
from pprint import pprint

cli_args     = sys.argv
file_name    = cli_args[1]
docker_image = cli_args[2]

with open(file_name, 'r') as data_file:
    data = json.load(data_file)
data_file.close()

data[0]['image'] = docker_image

with open(file_name, 'w+') as data_file:
    json.dump(data, data_file, indent=2, sort_keys=True)
data_file.close()

pprint('Docker image in file ' + file_name + ' has been updated to ' + docker_image)