Different YAML array representations

Question

I\'m writing a file type converter using Python and PyYAML for a project where I am translating to and from YAML files multiple times. These file are then used by a separate

Answer 1

As Jordan already pointed out the node style is a serialization detail. And the output is equivalent to your input.

With PyYAML you can get the same block style output by using the default_flow_style keyword when dumping:

yaml.dump(yaml.load("""\
key:
- value1
- value2
- value3
"""), sys.stdout, default_flow_style=False)

gives you:

key:
- value1
- value2
- value3

If you would be using the round-trip capabilities from ruamel.yaml (disclaimer: I am the author of that package) you could do:

import sys
import ruamel.yaml as yaml

yaml_str = """\
key:
- value1
- value2  # this is the second value
- value3
"""

data = yaml.load(yaml_str, Loader=yaml.RoundTripLoader)

yaml.dump(data, sys.stdout, Dumper=yaml.RoundTripDumper, default_flow_style=False)

to get:

key:
- value1
- value2  # this is the second value
- value3

Not only does it preserve the flow/block style, but also the comment and the key ordering and some more transparently. This makes comparison (e.g. when using some revision control system to check in the YAML file), much easier.

For the service reading the YAML file this all makes no difference, but for the ease of checking whether you are transforming things correctly, it does.