ExamplesΒΆ

Basic round trip of parsing YAML to Python objects, modifying and generating YAML:

from __future__ import print_function

import ruamel.yaml

inp = """\
# example
name:
  # details
  family: Smith   # very common
  given: Alice    # one of the siblings
"""

code = ruamel.yaml.load(inp, ruamel.yaml.RoundTripLoader)
code['name']['given'] = 'Bob'

print(ruamel.yaml.dump(code, Dumper=ruamel.yaml.RoundTripDumper), end='')

Resulting in

# example
name:
  # details
  family: Smith   # very common
  given: Bob      # one of the siblings

YAML handcrafted anchors and references as well as key merging are preserved. The merged keys can transparently be accessed using [] and .get():

import ruamel.yaml

inp = """\
- &CENTER {x: 1, y: 2}
- &LEFT {x: 0, y: 2}
- &BIG {r: 10}
- &SMALL {r: 1}
# All the following maps are equal:
# Explicit keys
- x: 1
  y: 2
  r: 10
  label: center/big
# Merge one map
- <<: *CENTER
  r: 10
  label: center/big
# Merge multiple maps
- <<: [*CENTER, *BIG]
  label: center/big
# Override
- <<: [*BIG, *LEFT, *SMALL]
  x: 1
  label: center/big
"""

data = ruamel.yaml.load(inp, ruamel.yaml.RoundTripLoader)
assert data[7]['y'] == 2

The CommentedMap, which is the dict like construct one gets when round-trip loading, supports insertion of a key into a particular position, while optionally adding a comment:

yaml_str = """\
first_name: Art
occupation: Architect  # This is an occupation comment
about: Art Vandelay is a fictional character that George invents...
"""

data = ruamel.yaml.round_trip_load(yaml_str)
data.insert(1, 'last name', 'Vandelay', comment="new key")
print(ruamel.yaml.round_trip_dump(data))

gives:

first_name: Art
last name: Vandelay    # new key
occupation: Architect  # This is an occupation comment
about: Art Vandelay is a fictional character that George invents...

Please note that the comment is aligned with that of its neighbour (if available).

The above was inspired by a question posted by demux on StackOverflow.