Value change with ruamel yaml won't work and ignores indenting

Question

I have a problem with dumping data back to YAML with correct format. Looked into other similar questions but didn't find solution for this problem. Current code in Python:

template = yaml.load(open(templateFile), Loader=yaml.RoundTripLoader)

template["key"] = new_value

yaml.dump(template, sys.stdout, Dumper=yaml.RoundTripDumper, indent=2)

Input:

parameters:
  key: value

Output:

parameters:
  key: value
key: new_value

Expected output:

parameters:
  key: new_value

How should the code be modified, to either change the old "key" value, or enter a new one with correct indenting?

Answer 1

You'll have to assign the new_value to the right mapping/dict:

import sys
from ruamel import yaml

template_file = 'input.yaml'
new_value = 'new_value'

template = yaml.load(open(template_file), Loader=yaml.RoundTripLoader)
template['parameters']['key'] = new_value
yaml.dump(template, sys.stdout, Dumper=yaml.RoundTripDumper, indent=2)

a new value indented "under" key would require:

template['parameters']['newkey'] = 'added_value'

please note that it is customary to use snake_case for Python variables like template_file (RoundTripLoader/RoundTripDumper are the names of classes)